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UNITED STATES DEPARTMENT OF AGRICULTURE
BUREAU OF PUBLIC ROADS
ROADS
Ih, all
WAG Le Tey INKen af Vv FEBRUARY, 1925
“OH, TO BE IN ENGLAND NOW THAT APRIL’S THERE, —’’
WASHINGTON : GOVERNMENT PRINTING OFFICE : 1926
PUBLIG ROADS
A JOURNAL OF HIGHWAY RESEARCH
U. S. DEPARTMENT OF AGRICULTURE
BUREAU OF PUBLIC ROADS
CERTIFICATE: By direction of the Secretary of Agriculture, the matter contained herein is published as administrative information and is required
for the proper transaction of the public business
VOLES NO A 12 FEBRUARY, 1925 H. S. FAIRBANK, Editor
TABLE OF CONTENTS
Page
Impressions of English Highway Practice . I
Percentage of Water Freezable in Soil ; 5
A Study of Motor-Vehicle Accidents in Montana, Oregon, and Washington Z : 7
Crushed Stone Tests and Their Relation to the Service of the Finished Pavement ara
Reinforced Concrete Pavement Survey : ; : ; a RS
Highway Research Board Reports Progress of Its Study
THE VU. S. BUREAU OF PUBLIC ROADS
Willard Building, Washington, D. C.
REGIONAL HEADQUARTERS
Bay Building, San Francisco, Calif.
DISTRICT OFFICES
DISTRICT No. 1, Oregon, Washington, Montana, and Alaska. DISTRICT No. 8, Alabama, Georgia, Florida, Mississippi, South Carolina
Box 3900, Portland, Oreg. and Tennessee.
DISTRICT No. 2, California and Nevada. Box J, Montgomery, Ala.
Bay Building, San Francisco, Calif. DISTRICT No. 9, Connecticut, Maine, Massachusetts, New Hampshire,
New Jersey, New York, Rhode Island, and Vermont.
Federal Building, Troy, N. Y.
DISTRICT No. 10, Delaware, Maryland, North Carolina, Ohio,
DISTRICT No. 3, Colorado and Wyoming.
301 Customhouse Building, Denver, Colo.
DISTRICT No. 4, Minnesota, North Dakota, South Dakota, and Wisconsin.
410 Hamm Building Se Panliving: Pennsylvania, Virginia, and West Virginia.
DISTRICT No. 5, Iowa, Kansas, Missouri, and Nebraska.
Saunders-Kennedy Building, Omaha, Nebr.
DISTRICT No. 6, Arkansas, Louisiana, Oklahoma, and Texas.
1912 F. & M. Bank Building, Fort Worth, Tex.
DISTRICT No. 7, Illinois, Indiana, Kentucky, and Michigan.
South Chicago Station, Chicago, Ill.
Willard Building, Washington, D. C.
DISTRICT No. 12, Idaho and Utah.
Fred J. Kiesel Building, Ogden, Utah.
DISTRICT No. 13, Arizona and New Mexico.
242 West Washington St., Phoenix, Ariz.
Owing to the necessarily limited edition of this publication it will be impossible to distribute it free to any persons or in-
stitutions other than State and county officials actually engaged in planning or constructing public highways, instructors in
highway engineering, periodicals upon an exchange basis, and Members of both Houses of Congress. Others desiring to
obtain “Public Roads” can do so by sending 10 cents for a single number or $1 per year to the Superintendent of Documents,
Government Printing Office, Washington, D. C.
IMPRESSIONS OF ENGLISH HIGHWAY PRACTICE
By A. B. FLETCHER, Consulting Highway Engineer, United States Bureau of Public Roads
This article by Mr. Fletcher, the first of a series, to be published
in Public Roads, dealing with his observations of English highway
practice, was prepared as a paper to be read at the T'wenty-second
Annual Meeting of the American Road Builders’ Association. In
it he presents in a pleasant and interesting way some of the more vivid
of his impressions gained in a visit to England in the spring of 1924.
In subsequent articles he will deal in greater detail with several of
the subjects to which he here refers.
URING THE spring of 1924 I was detailed to
D study the rural roads of England. With this
not unpleasant assignment was employed
during the months of April, May, and June, and
although England did not live up to her reputation for
fine spring weather—it rained nearly every day—
it was possible to get about without particular difficulty
even in the remote country districts. One could for-
give the raia for the astonishing beauty of the road-
sides which it produced.
In addition to meeting the English road officials,
the trip included a journey in a Chandler (American-
made) automobile from London to Edinburgh, and a
little farther north in Scotland, going up through the
counties on the east side of the Little Island and
returning to London by way of the westside counties,
a drive of more than 1,500 miles.
The main north and south roads were rather generally
followed, but the large centers of population and the
manufacturing cities were avoided for two reasons. I
wanted particularly to see the rural roads; and the
heavy traffic congesting the narrow, crooked streets
of the cities, built when riding in a saddle was more
popular than any other sort of transportation, was not
tempting to an amateur driver whose forbears for some
generations had been taught to drive on the right-hand
side of the street.
They say that even Henry Ford had to yield to
British conservatism and put the steering wheel on
the right-hand side before the English would buy his
cars. The Chandler car, originally made with the
steering wheel on the left side, had been remodeled so
that the wheel, clutch pedal, and brake were moved to
the right side. The gear shift, however, was left in
the center and had to be worked with the left hand.
One soon learned, to make the car go, but the idiosyn-
crasies of the car, together with passing other cars on
the wrong side of the road, made such a thing as intui-
tive driving out of the question. It was not difficult,
however, to go as fast as the law permits, for in England
as in Massachusetts the legal limit of speed is 20 miles
anhour. The law is obeyed equally well in both places,
I should say.
The journey, as it was planned, gave an opportunity
to inspect a considerable mileage of the two main
north and south trunk lines throughout the length of
England.
There are many similarities and some differences be-
tween the English country roads and the rural roads of
the United States. They are perhaps more crooked
even than the roads of our older States, and the reason
for the poor alignment is apparently the same in both
countries. In neither country was there any thought
of motor traffic or any other sort of fast traffic when
29956—25t——1
The narrow, crooked streets of the medieval cities, built when riding in a saddle was
popular, are not tempting to an amateur driver
the roads were surfaced. Mostly the roads were im-
proved by putting down hard surfaces within the limits
of the then existing rights of way. We seem to be
making faster progress in this country in correcting that
fault, perhaps not because we are more progressive,
as we like to think, but because the urge is greater.
The motors have come upon us at a faster rate and in
greater numbers, relatively, than in England.
Great Britain still has from 20 to 25 per cent of its
highway freight moved by horses, while I suppose that
in the United States not more than 10 per cent of the
traffic is horse-drawn, and in some of the States the
horses are no longer counted in the traffic census.
But when it comes to the matter of the riding qualit
of the roads we have very much to learn from Wngland.
I saw no road on my long auto journey so rough as are
most of our rural roads, but it should also be said that I
saw hardly any so smooth as the best of the roads in the
United States built by the State highway departments
with the Federal-aid stimulant.
THE ENGLISH AND AMERICAN ROAD PROBLEMS COMPARED
Our road problem is so much bigger than Great
Britain’s that the reason for the better average im-
provement of the English road is apparent. In all
England, Wales, and Scotland, there are but 177,000
miles of road, cities and boroughs included, as against
our estimated mileage of 2,941,000 outside of the cities
and towns. England, Wales, and Scotland have an
average of about 242 persons to the mile of road, while
in this country there are not more than 35 people to
themile. In Massachusetts, one of our States of dense
population, there are about 175 people to the mile.
The English roadside almost invariably is a thing
of beauty, and an American has to go to Scotland be-
fore he feels at home. For some reason, sparse popu-
lation and lack of money, perhaps, the Scotch road-
sides are nearly or quite as barren and unkempt as
(1)
On the whole we mark our roads better than the English. The rectangular object
at the right is a dust-covered mirror
most of ours are. The English 'roads generally have a
wide grass border, and there are trees and shrubs
everywhere. Sometimes the line of sight is restricted
by the roadside growths, but it is plain to understand
why even then the shrubs are spared.
The drainage water from the roads disappears
quickly from the carriageway and flows off in unseen
ditches near the right-of-way lines. The turf at the
pavement edge is carefully trimmed and kept so just
asin apark. Laborers trimming the edge with spades
with a tightly stretched cord for a guide were seen,
working as painstakingly as if they were trimming a
garden border.
The traffic control at bad road intersections in the
country as handled by the agents of the automobile
clubs, in cooperation with the police authorities, is
wonderfully well done and worthy of much more
attention than can be given to it here. In the matter
of road signs, however, 1 was disappointed. I think
that on the whole we mark our roads at least so far
as direction signs are concerned, better than it is done
in England.
Nearly all of the roads inspected were of some bitumi-
nous type, tar-mac, tar macadam, asphalt, tar-painted,
etc. In my 1,500-mile journey not more than a mile
or two of the road in the open country was recognizable
as being of the cement-concrete type, and some of that
had been covered with tar or asphalt. I do not imply
that no cement-concrete surfaces have been laid on
the rural roads, but seemingly most of the work of
that type must be in the cities and towns. The
English road officials from Sir Henry Mayberry, chief
of the road department of the Ministry of Transport,
down to the surveyors of the smaller counties seem to
be almost a unit in believing that they can not afford
to scrap the great mileage of bituminized roads which
they have constructed even if it can be proved that
the concrete type is more desirable from the viewpoint
of maintenance costs, which they seem to disbelieve.
They seem to be thoroughly wedded to the bituminous
types of construction.
The reason for their preference is clear when one sees
the carefully planned grades, long established, with
sodded shoulders, drainage ditches and entering drive-
ways, and when one realizes the great expense which
they have incurred in putting in the heavy road foun-
dations. Notwithstanding the large costs of maintain-
ing the bituminous road surfaces, the Englishman is
slow to adopt a road type with which he is not familiar,
and he is entirely willing that his American cousin shall
make what he calls the experiments. He wants proof
of the reputed low cost of maintenance of concrete
roads, and in his doubting conservatism he will not
admit that the relatively few years of life of the Ameri-
can concrete roads have given them any “history”
worth talking much about.
THE COST OF MAINTAINING ENGLISH BITUMINOUS ROADS
How large the upkeep charges are for the bituminous
roads is shown in some figures published by the ministry
showing the annual cost of oneae on four class 1 roads
leading out of London into the Provinces.t The total
length of the four roads is 321 miles and the report
Says:
i The annual cost of upkeep taken over the whole length of each
road ranges from £700 per mile in one case to £980 in another
($3,360 to $4,704 per mile).
Assuming the average width of the carriageway of
these roads to be 380 feet, and assuming that $4,000 per
mile fairly represents the average annual cost of up-
keep, we see that these four roads cost not less than
2214 cents per square yard for maintenance. This
annual outlay would appear to be sufficient to renew
completely the wearing surface as often as once in five
years. ‘The figures, the report says, do not include any
capital outlay for the roads in the past.
I have been unable to find a statement showing the
mileage or square yardage of concrete roads in Great
Britain. The handbook of the British Portland Ce-
ment Association states that 281 concrete roads had
been built up to June, 1923. Of these, nearly 79 per
cent were built after the year 1920. Many of the roads
were very short, some less than one-half mile in length,
and evidently the total yardage was not sufficiently
impressive to be set forth in the handbook.
On the other hand, much of the new arterial road
work in the vicinity of London is of the cement-concrete
type, some of it 50 feet in width with the slab 8 inches
thick, and the work very well executed, some American
equipment being employed.
There are so many types of bituminous road in use
or offered for use in England that the patentees have
had to tax their ingenuity to find names for them
all, but from my observation I believe that the
great builk of the pavements are either some sort of
penetration macadam, tar-mac, or merely surface-
painted.
I was much interested in looking for wavy condi-
tions or corrugations in the surface of the bituminous
roads. The county surveyors will tell one that they
have waves in their pavements, and they seem to
know what one is talking about when one speaks of
corrugations, but their waves are not like our waves,
for I found very little, practically no, evidence of the
corrugations which are so prevalent in our bituminous
pavements.
Their methods of spreading the bituminous material
are much like ours except that they work more slowly
than we do, perhaps more carefully and skillfully, but
1 Ministry of Transport
year 1922-23,
Report on the administration of the road fund for the
I am forced to the conclusion that the apparent super-
iority of the British bituminous roads is due very
largely to their thick, heavy foundations and in some
measure to the use of curbs to confine the pavements
at the sides.
Almost without exception the English road is built
with what they call “hard core” as a foundation.
Hard core may consist of almost any hard material
laid as a foundation for the full width of the carriage-
way. ‘The stones are large, sometimes as large as 8
inches in longest dimension and often as large as the
thickness of the layer will permit. The hard core
layer is usually from 8 to 12 inches in thickness. Strong
hard slag seems to be a popular material, but when
that is too costly and brickbats or stones from walls or
buildings are available they are put into the road.
The point is, of course, to secure a hard unyielding
base which will not hold capillary water. The county
surveyors are beginning to wonder if these hard core
foundations, strong as from our viewpoint they seem
to be, are going to be heavy enough for the future
motor traffic. When we consider how few of our rural
roads have any foundation at all under the 5 or 6
inches of bituminized stones, do we need to look much
further for the cause of the corrugations? Or to ex-
plain the apparent superiority of the British roads?
The English seem also to be completely convinced of
the need of substantial curbs to prevent the lateral
movement of the pavement. All of the new work with
which the Ministry of Transport has to do is provided
with curbs, and the county surveyors generally are
installing curbs in connection with their widening work
and extensive repairs.
BASES 12 INCHES THICK
Illustrating the extreme care in the matter of road
foundations which some of the county surveyors are
taking, C. F. Gettings, of Worcester County, told me
when I was looking over some of his work with him
that because of the bad subsoil with which he has to
deal, he first lays a stratum of ‘‘blinder,’’ or cinders, 3
inches thick over the subgrade, followed by a layer of
slag 6 inches thick, then a layer of 3-inch slag to a
thickness of 3 inches, then 3 inches of tar-mac, and
finally a dusting on the top of pulverized slag. ‘Thus
he has 12 inches of materiel in place before he lays the
wearing course, which he prefers shall be tar-mac.
Tar-mac is crushed slag, heated and mixed with a re-
fined tar at the works where the slag is produced and
shipped cold to the highway job.
When conditions permit him to do so, Mr. Gettings
employs what we in this country have come to call the
stage-construction method. First, after rolling as
much as is effective the 6-inch layer of slog, he turns on
the traffic to further consolidate it. He does the same
with the 3-inch slag layer, sometimes giving it a light
tar treatment and allowing the traffic to pass over it
for a considerable period, but not after it shows any
sign of distress. In this manner he makes sure, before
the wearing course is laid, that he has a firm, hard
base for it, and that there will probably be no further
settlement of his foundation after the pavement is
completed.
Some of the best bituminous pavements that I have
seen anywhere were built under Mr. Getting’s direc-
tion. The traffic over the main Worcester County
roads is called heavy. The country is in the Midlands,
English roads have a wide grass border, and there are trees and shrubs everywhere.
A pile of hard core material has here been left by the roadside
one of the regions of great manufacturing activity. The
traffic census taken by the ministry in August, 1923,
indicates that the roads are in the group of 1,000 to
1,500 tons per 16-hour day. We would not consider
that to be a very heavy traffic, but Mr. Gettings thinks
a carriageway 22 feet wide and of the thickness before
stated is needed for the main roads of the country
where the subsoil is bad.
THE COST OF ENGLISH LABOR
In the United States such substantial work would
cost much more than the public is accustomed to pay
for the rural highways. The English feel the high cost
of their road work, too. Common labor in 1924 was re-
ceiving the equivalent of 25 cents per hour, a price
which the English employer thought was outrageous,
yet we at that time were paying more than double the
English hourly wage. Living standards and cost of
living are different, but I do not believe the disparity
is so great as I had been led to believe.
In July, 1924, Portland cement cost in London about
$2.22 per barrel, American basis, and other materials of
construction seemed to be not greatly lower in price
than in the United States. .
The arterial roads near London are of great interest.
They are being built in part to supply the general need
for more roads, in part to by-pass through traffic so
that it will not have to go through the narrow, already
congested streets of the metro olis, and in part to pro-
vide work for the unemployed.
In England, in 1924, there were more than 1,000,000
ersons ‘‘on the dole,” or supported to a greater or
ess extent by the Government. Any public work
which could be found for these unemployed was wel-
comed, and for several years the construction of the
arterial roads in the Greater London area and the
by-pass roads around the cities and towns in the
Provinces has provided work for many men. In
1922-23 there was set aside more than $31,000,000
for the road-fund unemployment program.
In the Greater London area alone, 165 miles of the
arterial roads, including the widening and straighten-
ing of some roads, are either under construction or
planned for, the total estimated cost of the work being
in the vicinity of $60,000,000.
4
All of this work is being done on a large scale.
Rights of way 100 to 120 feet in width are being
secured and with much delay and difficulty. When
houses are in the way and must be demolished, the
public authorities must provide other houses else-
where to shelter the tenants, so great is the housing
shortage.
The carriageways of the most important arterial
roads are to be 50 feet wide and curbed. Sidewalks
and planting strips are provided for, and iron fences
are installed along the right-of-way lines. On the
Great West Road all pipes, sewers, water and gas and
all electric wires are to be placed in conduits under
the sidewalks and planting strips. One section of
this road under traffic in 1924 was said to have cost
at the rate of £180,000 ($864,000) per mile.
In the arterial road and by-pass work very low
grades are insisted upon, the alignment is as nearly
perfect as can be obtained, and no effort seems to be
spared in securing the best results in all branches of
the work. The pavements, or many of them, are of
the cement-concrete-base type laid in most instances
with the expectancy of covering them later on with
asphalt, but in some cases the concrete is being allowed
to take the traffic for the present. The concrete slab,
8 inches thick and reinforced, is said to be costing about
10s. per square yard ($2.40 approximately).
ENGLISH ROAD ADMINISTRATION
The Ministry of Transport took the place of the
road board in 1919, and under Parliament it is the
highest road authority of Great Britain. Its organiza-
tion is somewhat like that of the Bureau of Public
Roads. The road department of the ministry is in
charge of a chief, Sir Henry Mayberry, with Col.
C. H. Bressey under him in the capacity of chief
engineer who, in turn, has a corps of divisional engineers
located at various places throughout the country in
direct charge of the operations.
The revenue which the department has for road pur-
poses, derived almost wholly from the registration fees
paid on account of the motor vehicles, amounted in
1924 to about £15,000,000 ($72,000,000). This is
about the same sum that Congress has been appro-
priating recently for our Federal-aid work, but fae
the likeness ends. Colonel Bressey told me that the
annual revenue which the department received rep-
resented, fairly closely, one-third of the total sum spent
annually by Great Britain for all highway purposes.
Such a sum, approximately $216,000,000, would not
go very far toward paying the annual highway bill of
the United States, which in 1922 was estimated to
amount to more than $1,000,000,000.
The ministry has divided the roads into two cate-
gories, known as class 1 and class 2, and the present
policy is to allot to the counties not more than 50 per
cent of the cost of improvements on class 1 roads, and
not more than 25 per cent to such work on the class 2
roads. Roads less important than class 2 roads are
merely local in character, and they receive no money
from the ministry.
In England, Wales, and Scotland, the total mileage
of class 1 roads is about 23,000 miles, and the class 2
roads aggregate about 14,000 miles. The total mileage
of all roads, including the merely local ones, is given
as 177,321 miles, so, roughly speaking, the ministry
is concerned with about 21 per cent of the total mileage
of the country.
GASOLINE TAX ABANDONED IN 1921
Prior to January 1, 1921, at which time the present
road fund was established, there had been in effect a
tax on gasoline or ‘‘motor spirit,” speaking in the lan-
guage of the country, by means of which most of the
grants made by the ministry were financed. After the
year 1915 this tax was at the rate of 6 d., about 12
cents per gallon. Beginning with January 1, 1921, the
tax was abolished, and in place of the gasoline tax as a
revenue producer a tax of £1 (about $4.80) per horse-
power of the motor vehicles was substituted.
This tax is still in effect, and the owner of a Ford car,
for example, pays into the public treasury annually
very nearly $100 for the privilege of driving on the
British roads. The high registration fee has fostered
the manufacture and use of low-powered cars, and
special attention has been given to small-cylindered
motors and high piston speeds.
The ministry does not favor a proposed plan to
return to a gasoline tax, which the motor interests are
pressing for, chiefly, I believe, because the officials
dislike to abandon a source of assured income for a
plan which they think to be less sure. They say they
need at least £15,000,000 per annum for the roads;
that the present taxing plan will surely produce that
revenue; and that their experience with the collection
of the gasoline tax prior to 1921 has not left happy
memories. The old relatively high gasoline tax was
doubtless evaded in many instances. Sir Henry May-
berry says that while the motors were increasing 1n
numbers from year to year in an astonishing fashion
the receipts from the tax remained nearly constant.
Much of the gasoline and the kerosene imported into
England nominally for heating and manufacturing
purposes doubtless found its way into the tanks of the
motor cars.
To conclude this somewhat sketchy and superficial
summary of some rather large subjects, I believe that
in speed of road construction, in the matter of road
equipment of all kinds, as concerns motor-vehicle regu-
lation, highway financing, and research and experi-
mental work generally, we do not have much to learn
from Great Britain.
In matters of road location we can see there in aggra-
vated form the same sort of mistakes which have been
made in this country, particularly in the older States,
where we have put down expensive pavements on
faulty locations with unnecessarily tortuous alignment,
a timid following of the line of least resistance, usin
rights of way good enough, perhaps, when horses di
the work but sadly inadequate for our present-day
motorized traffic.
It is doubtful if we can hope to equal the bituminous
roads of England until we pay more attention to the
foundations. We should either follow somewhat after
the English methods or develop some substitute, pos-
sibly less costly, which will be as effective.
5
PERCENTAGE OF WATER FREEZABLE. IN SOILS
By A. M. WINTERMYER, United States Bureau of Public Roads
ECENT experiments by the United States Bureau
R of Public Roads to determine the percentage
of water that will freeze at ordinary freezing
temperatures in various typical soils have shed new
light on probable relations between certain distin-
guishable characteristics of the soils and the percentage
of their contained water that can be frozen.
When a soil “‘freezes,”’ i. e., when water contained in
thesoil is frozen, the freezing very seldom involves all the
water in the soil. Most soils contain some percentage
of water, which may be large or small, depending upon
the nature of the soil, that will not freeze at tempera-
tures immediately below the freezing point of water;
and in some soils a portion of the contained moisture
can not be frozen even at temperatures below —78° C.
If the soil be frozen in a dilatometer, using the
method employed in the recent Bureau of Public Roads
experiments, which will be later described, the water
content can be divided into three volumes determined
by the temperature at which they are frozen. The
first volume, which will be frozen at 0° C., is classified
as free water; the second, which will freeze at from
—4° C. to —78° C., is classified as capillary or adsorbed
water; and the third, classified as combined water, is so
intimately associated with the soil that it can not be
frozen even at temperatures below —78° C. Different
soils differ widely in the percentages of their contained
water which fall into these three classes. In some the
entire water content can be frozen at 0° C. or slightly
below. Clean standard Ottawa sand is such a soil.
In other materials, especially those high in soluble
salts, with which the contained water combines, the
percentage of such salts may be so large that no part
of the water may be frozen even at very low tem-
peratures.
As the freezing of water in the soils composing road
subgrades, with the accompanying phenomenon of
heaving or swelling, is one of the most troublesome of
highway problems, it is decidedly worth while to ascer-
tain what properties of the soil affect the percentage of
the contained water that may be frozen, for by doing
so it is possible that means may be found to alter these
roperties in such a way as greatly to reduce the trou-
Pleads freezing. Yet very little work has been done
along this line; indeed, the only published information
that has been discovered is that contained in Technical
Bulletin No. 36 of the Michigan Agricultural College,
by George J. Bouyoucos.
PERCENTAGE OF WATER FROZEN CLOSELY RELATED TO DYE
ADSORPTION VALUE OF SOIL
The principal results of the recent experiments by the
Bureau of Public Roads are the indication of a fairly
close relation between the percentage of water frozen
at —1.5° C. and the dye adsorption number of the soil,
and the perfecting of the dilatometer method by which
the percentage of water frozen may be determined with
reasonable accuracy.
It appears as a general rule from these tests that the
percentage of water in soil freezable at —1.5° C. in-
creases as the dye adsorption number of the soil de-
creases. Apparently the adsorption of dye and the
water frozen are both controlled by the same properties
of the soil, namely, the chemical composition, colloidal
content, mineralogical SOS OL Oar con-
tent, percentage of soluble and insoluble salts, etc.
The presence of certain constituents or properties which
give the soil a high adsorption number causes also the
removal of a certain amount of water from the active
state, so that the freezing point is lowered very con-
siderably, allowing only a small percentage to be frozen
at —1.5° C. In a number of instances in the recent
experiments the percentage of soluble salt was so large
that no moisture was frozen in the soil even after lower-
ing the temperature to —20° C.
There seems to be a tendency also for the percentage
of water frozen to be greater in coarse-grained than in
fine-grained soils; but to this tendency there are many
exceptions. The mechanical analysis may show a
large percentage of coarse material, yet only a small
amount of moisture may be frozen. The mechanical
analysis shows only the arbitrary size of the soil par-
ticles, and not their real condition as, for instance,
whether the particles are crystalline or colloidal, etc.
A much closer relationship seems to exist between the
adsorption number and the moisture frozen; and this
is not surprising when we consider that the same factors
control both the dye adsorbed and the moisture frozen.
‘The experiments show also that moisture does not
freeze with the same speed in different soils. In
some soils the freezing is very rapid; in others very
slow. The real freezing point is not at 0° C., but some-
eh owes in some cases it was found to be below
Since the dilatometer method, as perfected in these
experiments, accurately shows the amount of free or
active water in the soil, it would seem advisable to
determine this amount of water in the soil in conjunc-
tion with the regular soil analysis. It is this water
that gives rise to the troubles so often encountered
during the freezing season. After the active water has
been determined in a particular soil and found to be
high in amount, methods may possibly be devised to
remove the greater part of this water from the active
state by Aner some suitable material that will form
a combination with it, and lower the freezing point
considerably. This would greatly decrease the amount
of water frozen and minimize the danger of upheavals.
THE RESULTS OF THE TESTS
In an earlier series of tests, conducted in 1922, the
various soil samples were treated with the same amount
of water, 5 cubic centimeters in all cases. It was found,
however, that this quantity would not moisten the
entire sample in all cases. It was decided therefore at
the commencement of these tests to try the use of
several percentages of water with respect to the volume
of the soil, corresponding to the moisture equivalent,
and the percentages obtained in the vertical capillarity
and water-holding capacity tests,! and to run a suffi-
cient number of tests to determine which would be the
most favorable percentage for use. On the basis of
these trial tests, the percentage of moisture corre-
sponding to the indication of the vertical capillarity
test was finally chosen for use in the subsequent tests.
The results of the tests on the various soil samples
treated in this way are shown in Table 1, which gives, in
addition to the quantity of moisture added to the soil
and the percentage frozen, the mechanical analysis and
the absorption number of the soil.
1 For descriptions of these tests, see PUBLIC Roaps, vol. 4, No. 3, July, 1921,
6
Tape 1.—Relation between mechanical analyses and adsorption TAsiE 1.—Relation between mechanical analyses and absorption
numbers and water frozen in various soils
numbers and water frozen in various sotls—Continued
t
Total | Adsorp-
+ Total : Water Water Water
Soil No. fine tion
sand | material | number | added frozen frozen
Cubic Cubic
} | centi- centi-
| Per cent | Per cent | meters meters Per cent
3 | 38. 8 | 61. 2 | 15.0 | 6.5 3. 45 53. 0
52.0 | 48. 0 35. 0 | 6.0 3. 60 60. 0
70. 4 | 29. 6 | 7.5 4.0 | 2. 90 72.5
41. 2 58. 8 | 22. 5 | 6.5 | 4.70 72.3
12.8 | 87. 2 | 40. 0 | 7.6 | 4. 00 53. 4
2.5 | ray 30. 0 | 7.6 4. 05 54. 0
4.4 95. 6 22. 6 | 7.0 4. 50 64.3
1.6 84. 4 22. 5 | 7.0 | 4. 20 60. 0
31.2 68. 8 8.3 | 5.5 3. 30 60.0
37.6 | 62. 4 | 17.5 | 7.0 4. 50 64.3
12.0 | 88. 0 | 17.5 | 8.0 6.15 70
26. 8 73. 2 55. 0 | 8.0 3. 80 47.5
26. 4 73. 6 22.5 7.0 4. 30 61.5
34. 0 66. 0 80. 0 | 7.5 4, 00 53. 4
88.1 | 11.9 | 11.0 7.0 5. 40 77.2
28. 4 | 71.6 15.0 5.5 | 2. 45 44.5
9. 2 90. 8 | 130. 0 cfm) 1.70 24.3
18.0 82. 0 90. 0 | 7.5 | 3. 60 48. 0
47,2 52. 8 | 67.5 8.5 5.35 63. 0
22. 4 | 77.6 | 90. 0 | 9.0 5. 20 57.8
28. 4 | 71.6} 150.0 | 10.5 3. 20 30. 5
15. 2 | 84. 8 158. 8 9.0 | 3, 60 40. 0
20.8 79. 2 | 127. 5 | 8.5 | 3. 74 44.0
22. 0 | 78. 0 | 45.0 6.5 4. 00 61. 5
66. 0 | 34.0 | 25.0 6.0 4, 24 70.7
13. 2 | 86. 8 100. 0 | 8.5 3. 10 36. 5
53.6 46.4 | 42. 5 | 6.0 2. 85 47.5
3.6 | 96. 4 | 90. 0 | 9.0 5. 30 58.9
41.6 58. 4 | 31.3 8.0 | 3, 70 46.3
23. 2 76.8 | 55.0 | 8.0 4.00 50. 0
90. 4 | 9.6 | 7.5 | 5.0 | 2. 55 51.0
40. 0 60. 0 | 30. 0 | 7.5 3. 60 48. 0
46. 8 53. 2 | 16.3 9.0 3. 20 35.6
8.4 91.6 | 120. 0 | 17 5. 30 45.3
8.8 | 91.2} 182.5 8.0 | 2. 00 25.0
18.0 82.0} 140.0 | 8.0 | 2. 65 33. 1
17.6 | 82. 4 | 38.8 9.0 5.00 55.5
38. 0 | 62.0 | 52.5 7.0 4. 00 57. 2
a0} 99. 1 | 52. 5 8.0 | 4. 40 55. 0
14, 4 | 85.6 | 55. 0 7.0 4. 00 57.2
6.0 | 94. 0 | 18.8 8.5 5. 90 69. 4
8.8 | 91.2 | 40.0 | ao 5. 20 69.3
12.0 | 88. 0 | 87.5 | 8.5 5. 40 63. 5
16, 0 | 84. 0 | 130.0 | 9.0 4, 80 53. 4
2.6 | 97.4 | 55.0 | 8.0 | 2.10 26.3
31.6 | 68. 4 | 22. 5 | 6.5 4.05 62.3
55. 2 | 44.8 | 35.0 | 8.0 4. 55 57.0
7.2 92. 8 87.5 11.0 | 6. 60 60. 0
p 4.5 95.5 | 95.0 8.5 4,70 55.3
5 9.0 91.0| 85.0 | 9.0 6. 00 66.7
14.4 95.6 | 20. 0 | 8.0 5. 35 66.9
, 1.6 | 98. 4 | 50. 0 10.0 5.75 57.5
e Se ee ee Et eee Ree (Pe a ae oe | 6.5 2. 60 40.0
of | | + fr
1, cena idan Miia reuters aT Me)|, 0 veenl ort
Ee te 94.0 6.0 | 2.5 | 4,5 3. 40 75.6
EE a eee 43.6 56.4 | 35. 0 | 8.0 4.30 53. 8
LOS oper fect eee oe 78.4 21.6 | 15.0 | 5.0 3.75 75.0
oie Fe pticler hove seer ae 73. 2 | 57.5 | 8.0 5. 60 70. 0
BAT Gao. cat mateo eee 10.0 Bo i haey a8 . = tee
= Qo eae 4 ov, | . ras ° Dee
29 aoe Fe ey ae 74. 4 25. 6 | 6.3 5.0 4, 20 84.0
291 Siete eee 65.6 34. 4 | 7.6 | 5.5 3.25 59.1
292 Le ands een Soe 30, 0 70. 0 | 32, 5 13.0 6, 20 47,7
293 tpeta dese ESE 74.8 25.2 | 7.5 5.0 4.05 81.0
294 SO Ra ey 77.6 22.4 | 30. 0 5.0 3. 45 69,0
BOS. ate sue bhteactecd 30.6 | 69. 4 | iH 9.0 4.00 44.5
324 ies. SH: 16.5 83. 5 17.5 | 10. 5 5. 30 50.5
ao ee ar alt, Seah Seek ieee eee ae
BO stn en nbssred 9. ¢ 0.1 | 5 8.0] 4.10 51.3
327 na Chapa dp ROMA 52.8 47.2 | 12.5 8.0 4, 20 52.5
328. ---------------- 54,1 45.9 | 10. 0 9.0 5. 90 65.5
V4) fete Bicep Ae peel 24. 2 | 75.8 | 13.8 9.0 4.90 54.5
BI seeds ates seen 15.8 84,2 | 32.5 | 8.0 0 10
Co eee 3.1 | 96. 9 | 57.6 | 10.0 0 10
O18 2 ee ER 6.4 93.6 | 25.0 9.0 0 10
WIRE Cee ey Se BE: 27 97.3 | 40. 0 10.0 0 10
au BW Gar letras te Sa ae: 7.5 | 92. 5 | 43.8 | 9.0 0 10
415. -naewananenann4s $3) 967 / 50.0) 110 0 10
6-.---------------- 4 | 96.6 | 68.8 | 10.0 0 10
Ree eta Ea - 15.1 | 84.9 | 38.7 | 10.0 0 10
pe ee ier ane. Leena ee ‘0
1 a Ny eo 3. 76. 0 | if 0 0
Magne age ae ioe; soa) acs| sel o 10
OF ee En . 6 | f i ; 0
NOS. itsintonanveticees 2.5 | 97.5 32. 5 | 12.0 0 10
= suring SoRuee, ears 5.6 94, 4 32.5 10.0 0 10
962i rs] ole ort) sel Pinel tp 19
ER AES EP: a7 96. 3 50.0 9.0 0 10
Pe OS Deke A Lae 14| 986] 67.5 | 12.0 0 10
$02 i nick ddlcen sents 10.8 | 89. 2 | 90. 0 | 9.0 0 10
Re eee eee. 7.2 92.8 | 43.8 | 10.0 0 10
$96. aa nn onneanne 72.0} 28.0 10. 0 6.5 3. 00 46. 2
wc ee grat) isal © teedle Rd, eine
1p aie EE Lh , j ; ; ih 62.
rc Ni scien ees Te ey ek
eS aaa oy, at ‘pF 5 0 | 4 De
500. was eaves wesncn an 69. 9 | 30. 1 7.0 | 5.0 2.70 54.0
502 Se ea 68. 1 | 31.9 9.0 | 5.5 2, 40 43.6
1), SO ON bo hed 71,2 28. 8 3.0 | 5.0 3. 70 74. 0
Total | Adsorp-
Total : Water Water Water
Soil No. sand eerial ee added | frozen | frozen
}
Cubic Cubic
centi- centi-
Per cent | Per cent meters meters Per cent
53.4 46. 6 10.0 | 5.5 3. 20 58. 1
52.0 48.0 11.0 6.0 3. 60 60. 0
84. 2 15.8 2.0 4.0 3. 00 75. 0
88.7 11.3 2.0 4.0 3. 20 80. 0
64.9 35. 1 3.0 4.0 2. 40 60. 0
63. 2 36.8 6.5 4.5 2. 30 51.1
63. 8 36. 2 9.0 6.0 4. 50 76:0
63. 6 36. 4 6.0 4.5 2. 90 | 64.5
55. 2 44,8 11.0 6.0 3. 00 50. 0
53. 2 46.8 5.5 4.0 2. 30 57.5
‘: 48.4 51.6 4.0 4.5 2.90 64. 5
PAY een eae ee 72.5 27.5 2.0 3.5 2. 00 57.2
a ee ee ee 63. 2 36. 8 4.0 4.5 3.40 | 75.6
AD one ee ag cree tees 68. 9 31.1 6.0 4.0 2. 80 | 70. 0
BABI cee ea ee 43.0 57.0 10.0 6.0 3. 40 56. 7
BBU obese tec cme eee sous 43.6 56. 4 13.0 6.0 3.10 51.7
bO2 Sec e st etoecoees 35. 4 64. 6 22. 0 8.0 4. 30 53. 8
Vile ee eee on os SS ee 61.9 48.1 16. 0 6.5 3. 70 56. 9
lif of Rete, te eee ee 44.8 55.2 13.0 6.0 2. 40 40. 0
POO. co See eeeeee 52.9 47.1 14.0 8.0 4, 00 50. 0
5/0 ee wenoremeuee ee. 56. 2 43.8 12.0 6.0 4. 50 75.0
Bile Sen oe aera S| 74, 2 25.8 8.0 4.5 3. 90 | 86.7
BT coe eee 65. 0 35. 0 6. 0 5.0 3. 60 72.0
Sot tee eee ee 64. 6 35. 4 27.0 7.0 3. 50 50. 0
DESI Pee ae ee a= 71.0 29. 0 8.0 4.0 3. 20 80. 0
SOl au. ce ateeeneencs 76. 6 23.4 7.0 4.0 2. 80 | 70. 0
BOD. Ue ee ee ae 68. 2 31.8 16. 0 5.0 3. 00 60. 0
593.272 o. eee 64. 8 35. 2 11.5 4.0 1. 60 40. 0
DUG se @ece Sete cee 56. 7 43.3 8.0 4.5 3. 00 66. 7
if VR De oR eae BS 64. 6 35. 4 7.0 9. 0 6. 30 70. 0
VAl Se aes aaa 76.7 24.3 alee ay | 9. 5 3. 80 40.0
WA Se Soe te eee 62. 7 37.3 ey 11.5 Ba0 32. 2
(fees fo Pe 52.8 47.2 19.0 9.0 4. 00 44.5
Ao ee ae, re Se 61.4 38. 6 4.0 8.0 5. 60 70.0
phe oe ve et 71. 5 | 28.5 4.5 9.0 6. 90 76. 7
fv Rae ee a ees 15.9 84.1 23. 8 15.0 6. 70 44,7
(boson sdeseseeteeenes 49.7 50.3 Aloe. 4.0 . 80 20. 0
OGs Jeet coeat ane see 2.9 97.1 55. 0 11.0 0 10
iy Pee eee 3.4 96. 6 68. 7 11.0 0 10
DOs oe ee ee eee 6.9 93.1 32. 5 10.5 0 10
el rs Roel ee Ber Se 6.6 93. 4 40. 0 9.0 0 10
VOUS Qiks ee eee PEP 97.8 50. 0 10.0 0 20
(61 eS ee te 3°38 96. 7 35. 0 10.0 0 20
i i ee eee mens Qi) 97.9 40. 0 11.5 0 10
163 22 eo a eee 3.8 | 96. 2 31.3 9.5 0 10
700 coe Se dub ce eee ae 10. 7 89.3 7 fi) 8.0 3. 60 45.0
(i Re ene rae 19, 4 80. 6 42.5 8.0 4.10 51.3
Quartz sand -.__.._- 1002 OY teen ached cawan ame =(eeceee Sate tere 100. 0
1 These soils were all from the Great Salt Desert in Utah. They contain varying
percentages of salt, all so high that all water mixed with the samples undoubtedly
combined with the salt, so that none of it could be frozen at —1.5° C.
2 These soils were from Nevada and were similar to the Utah soils,
Considering the data in Table 1, it will be seen that
the amount of water frozen varied from 100 to 0 per
cent. The quartz sand, however, was the only soil in
which 100 per cent was frozen, and upon grinding this
standard Ottawa sand into flour only 70 per cent of
the added water was frozen. This seems to indicate
that the size of the particles is one of the controlling
factors in the amount of water frozen; and, as a general
rule, it will be observed that the percentage of water
frozen does increase from the fine to the coarse-textured
soil. But while there is such a general tendency there
is apparently no definite relation between the mechani-
cal analysis and the percentage of water frozen. For
example, soils Nos. 5, 201, 290, and 298 all have a
high percentage of coarse material and show a high
percentage of water frozen. Soil No. 38 is practically
all coarse material, yet less of the contained moisture
was frozen than in some of the soils which contained:
only a small amount of coarse material, as, for example,
soils Nos. 9, 10, and 59. Soil No. 20 is composed of a
lerge percentage of fine material, and only a small
amount of the water was frozen, thus conforming
more closely to the general rule than the majority of
the soils.
The fact is, of course, that many factors must be
considered as influencing the percentage of water that
can be frozen at —1.5° C., since soil is more often
heterogeneous than homogeneous. <As a rule the con-
dition of the moisture and the temperature at which
it will be frozen depend upon the physical, chemical,
and mineralogical composition of the soil. Soluble
salts, organic matter, and colloidal material present
will remove a certain percentage of the moisture from
the free state and prevent its freezing.
MECHANICAL ANALYSIS DOES NOT INDICATE FREEZING
PERCENTAGE
The mechanical analysis merely shows the size of
the soil particles, while the water unfrozen is an index
not only of the size of the particles but of other prop-
erties as well. Since the adsorption number of the
soil indicates in the main the same _ properties, it
might be expected that a relation would exist between
the adsorption number and the percentage of water
frozen; and, in fact, such a relation is evident in the
results of the tests, as will be observed by reference to
Table 2, in which certain of the data from Table 1
are arranged in the descending order of the percentage
of water frozen.
TaBLe 2.—Comparison of percentage of moisture frozen and
adsorption numbers of soils
Moisture frozen |Adsorption number Clay content
Soil No. ov ’
ac | Fae Each
sample Average sample Average sample Average
os —— = i = | | ea 2. | = =
Per oa Per cent nn Per cent | Per cent
’ ; : 16.0 .
ap 8b { 68 6.9 { 10 \ 15,8
fot) 17.5 46.0
75.6 ! 2.5 6.2
75. 0 15.0 15.9
72.5 7.5 11.6 | 2
72.3 72.9 22.5 20. 3 32.0 25.1
70.7 | 25.0 29. 3
70. 0 | 57.5 40. 4
70. 0 15. 0 20. 4
69. 4 18.8 28. 0
69. 3 | 40.0 34.8
69. 0 30. 0 13.6 |
67.2 25.0 18.0
66. 9 20.0 45.6
64.3 Goole 17. 5 31.8 36. 8 35. 9
63. 5 | 87.5 71.8
63.0 els 40.8
62.3 : 22,5 41.8
61.5 2005 41.6
60. 0 8.3 22.4
59.1 | Co 19, 2
57.8 j 90. 0 52.8
57.5 50. 0 76.5 i}
St. 2 ae Pa 5
57.0 3. 2.
55. 5 55.8 38. 8 60. 4 38, 8 | 42.5
55.0 | 52, 5 33.8 |
53, 8 35.0 | 35.0
53. 4 | 180.0: 55.6
52. 5 : 110.0 | 45.6
48.0 90. 0 56. 8
47.7 32:6 | 63. 1
47.5 ' 42.5 | oo.
47.5 | 55. 0 48.8
46.3 45.6 ° Biles || 74.7 36. 4 51.4
45.3 120.0 | 82.0
44.5 15.0 | 29.6
44.0 WP ta) 52. 0
40. 0 | 158. 8 ae
Comal 140. 0 1.6
30. 5 } ale { 150, 0 \ ee { 45.7 \ 58.7
Even in the data for the individual soil samples in this
table there is evident a general relation. Comparing
the average values for the several groups, this relation
becomes more apparent, for these values show very
definitely that as the adsorption number and the clay
content of the soil increase the percentage of moisture
frozen decreases. Several of the individual values
depart from the rule, but no more than one would expect
in dealing with a relation in which there are involved so
many factors. In this connection the fact that certain
classes of dyes are adsorbed more readily by some kinds
~~
of soil than by others must also be taken into considera-
tion. The chemical composition of the soil has a great
deal to do with the adsorption. Acid dyes, as a rule,
are more strongly adsorbed by basic minerals and soils
than are basic dyes, and vice versa. In cases where
ummonia exists in the soil as a salt the adsorption may
be increased in some instances; in others decreased by
the presence of the salt. In these tests methyl violet,
au basic dye, was used; and it is quite probable that
some of the departures from the general rule in indi-
vidual samples may be attributed to the basic proper-
ties of the dye. Certainly, one would expect that the
basic soils would show a relatively lower adsorption
number than the acid soils.
TEMPERATURE WHICH SOILS MAY ATTAIN WITHOUT BEING
FROZEN
It is known that pure water may be easily cooled to
—3° or —4° C. without the appearance of ice if kept
quite still while the temperature is reduced. Whaile
conducting the freezing experiments it was decided to
determine the temperature to which the soils could be
lowered and yet remain unfrozen. |
The procedure was the same as in the other tests
except that the temperature was steadily lowered in-
stead of being maintained at —1.5° C., and the soil was
left undisturbed in the freezing mixture. ‘The results
obtained showed that all the soils thus treated, about 20
in number, remained unfrozen until the temperature
reached —4° C., when they automatically froze. The
soil, however, may be kept in the surfused or under-
cooled condition an indefinite length of time, and the
process of solidification can be started by the slightest
vibration or movement. This shows that the soil may
very often remain unfrozen even though the tempera-
ture be below the freezing point.
EFFECT OF HEATING ON THE AMOUNT OF WATER FROZEN
With a view to determining the effect of heating on
the amount of water freezable in the soil samples of a
red clay soil were heated to temperatures of 100, 200, 300,
400, 500, and 600° C., respectively, and maintained at
these temperatures for one hour, after which water was
added in amounts corresponding to the vertical capillar-
ity percentage, and the wet samples were frozen. The
heating changed the color of the soil from a light red at
100° C. to a dark brick red at 600° C., and the plastic
properties of the soil decreased with increase of tem-
perature.
At 100° and 200° C. the soil was very plastic and
froze after considerable agitation at —1.6° and
—1.5° C., respectively. The time required for com-
pletion of the freezing process after it commenced was
in each case 50 minutes.
At 300° C. there was a slight decrease in the plasticity
of the soil and the color changed to a slightly darker
red. Freezing commenced at —1.5° C. only after con-
siderable agitation, and the time required to complete
the process was 60 minutes.
At 400° C. the soil was less plastic and turned to a
dark brick red. It froze readily at —1.5° C., requiring
50 minutes.
At 500° C. the plastic qualities were destroyed, the
color remaining about the same as that heated to
400° C. The soil froze readily at —1.5° C., and the
time required was 1 hour and 30 minutes.
At 600° C. the soil was nonplastic, the color becom-
ing a shade darker. It froze readily at —1.5° C. and
required about one and three-quarters hours.
APPARATUS AND METHODS EMPLOYED IN THE TESTS
Tho apparatus employed in the experiments con-
sisted as shown in Figure 1, of a bath, A, dilatometer,
D, and potentiometer, C. The typo of dilatometer
used had a removable stem with ground joint, as
shown in Figuro 2. This facilitated the handling and
cleaning of the apparatus and removed one of the
chief causes of breakage. The dial of the potentio-
meter used to record the soil temperature was so grad-
uated that the potential difference could be read in
¥
«
==
yi
Fic. 1.—Apparatus employed in the dilatometer test
tenths of microvolts. With this arrangement the
temperature was controlled to within one-tenth of a
degree. For controlling the cold junction temperature
an ordinary thermos flask (fig. 1, B) was provided.
The temperature bath consisted of two earthenware
jars (fig. 1, A) placed one inside the other. The outer
jar was of 3 gallons capacity and the inner of 1 gallon
capacity. The space between the two jars was packed
tightly with hair, the upper part being made water-
proof by a layer of paraffin. The cooling mixture con-
sisted of crushed ice and salt.
In the preliminary tests conducted in 1922 great diffi-
culty was experienced in obtaining concordant results.
The variation in some soils was so great that the data
obtained were of no value. ‘This variation was found
to be due chiefly to the nonuniformity of the sample.
Another factor found greatly to aid in obtaining close
checks was to let the sample stand overnight and thus
insure a more equal distribution of the water added.
This method was followed during the final work.
The method of quartering as used is as follows: An
aliquot sample of air-dried soil, about 500 grams,
was mixed as thoroughly as possible and then quar-
tered. Two opposite quarters were then. mixed to-
gether thoroughly and again quartered. This procedure
was continued until about 25 grams of the original
sample remained. This was then thoroughly mixed
and the required 25 grams weighed. By following this
procedure and by allowing the wet soil to stand over-
night very close, and in some cases, perfect checks were
obtained. As already stated, the amount of water
added in the recorded tests corresponded to the vertical
capillarity percentage.
The main procedure was as follows: To 25 grams of
air-dry soil the required amount of water was added.
The soil and water was thoroughly mixed in the
dilatometer. The thermocouple and stopper were
then inserted into the neck of the bulb and sealed
and allowed to stand overnight. Ligroin or petroleum
af was then added through the stem, so that the
bulb was just completely filled. The dilatometer was
then mildly jarred to set free any air bubbles held b
the soil. Finally gentle suction was applied, tel
quite completely exhausted the air from the soil. The
air was excluded from the bulb by filling it and letting
the air escape at the bend. When no more air could
be expelled, the stem was filled with ligroin and covered
with a paraffined cork cap to prevent volatilization.
The ligroin was used to fill the bulb and act as an
indicator, because it is not miscible with water. _
The bulb of the dilatometer was then placed in the
freezing bath and the soil allowed to supercool to
—1.5° C. When this temperature was reached, the
water in the soil was caused to freeze by gently moving
the dilatometer in the freezing mixture until solidifi-
cation commenced, which was indicated by the rise
of the ligroin in the stem. The bulb was allowed to
remain in the bath, with frequent shaking, until the
rise of the ligroin ceased. The total rise represented
the total amount of expansion due to the formation of
ice. This water frozen at --1.5° C. is regarded as free
water.
In order to determine the factor for converting the
volume of expansion due to the formation of ice, 5
cubic centimeters of distilled water was added to
25 grams of clean, dry Ottawa sand. Upon freezing
this gave an expansion of 0.5 cubic centimeter, showing
that ‘1 cubic centimeter of water will expand 0.1 cubic
centimeter upon freezing. This value corresponded
to that obtained in the experimental stage of the work.
The time required to complete a determination
varied with the class of soil. The speed of solidifi-
cation at —1.5° C. is very low_and the greatest amount
of time consumed is after crys-
tallization commences. It
varies from one-half hour to
two hours.
In order to obtain concord-
ant results and eliminate trou-
ble, certain precautions must
be observed. The sample
should always be thoroughly
mixed so that the quantity
used will represent a uniform
mixture of the whole. As
nearly as possible the soil
should be allowed to attain the
same supercooling tempera-
ture. ‘There is little danger
of premature solidification at
—1.5° C.
The ice bath should be kept
dry and constant, at least
within 1° below the required
temperature. This can be ac-
complished by siphoning off
the water collecting at the bot-
tom of the bath.
Most of the trouble experi-
enced is due to the cork stop-
ers. These do not always
orm a tight connection with
the neck of the bulb, because — =
of internal unsoundness of the __- Fic. 2—Modified dilatometer
cork or small cracks on the —
side. It is always best to use sound corks, because the
ligroin will be forced through these internal or external
openings by the pressure within the bulb and will loosen
the paraffin seal. Should this happen, it is better to
use a new cork than to try to renew the seal, because it
is seldom accomplished. The sides of the corks should
also be examined for paraffin. If any is found, it
should be removed, because it will be dissolved by the
ligroin and allow it to reach the seal and escape.
4)
A SITUDY OF MOTOR-VEHICLE ACCIDENTS IN
MONTANA, OREGON,
AND WASHINGTON
By A. C. ROSE, Associate Highway Engineer, United States Bureau of Public Roads
TATISTICS of highway accidents involving motor
S vehicles which seem to point clearly to congestion
of traffic as the principal cause have recently been
compiled by the writer from newspaper reports of acci-
dents in the States of Montana, Oregon, and Washine-
ton during the greater part of the period from Decem-
ber, 1923, to September, 1924. A classification of the
reports, procured from State-wide newspaper clipping
services, indicates the relative importance of other
causes, such as speed, recklessness, and carelessness
ie) \ 2 3
WASHINGTON.____._____. S27 :
GORIEGON: .....s20nce-c ence eee
MIONITAINA= eee cc cccec cee 8 te
Fic. 1.—Number of accidents per 1,000 motor vehicles
or incompetence of drivers, intoxication, mechanical
breakdowns, faulty highway conditions, etc., but
these seem to be secondary causes which augment the
fundamental condition.
The most striking fact revealed by the compilation
is that the accident rate per 1,000 motor vehicles is
lowest in Montana, in which the number of motors
vehicles registered is lowest, and is higher in the other
two States in almost direct proportion to the number
of vehicles registered in these States. This indication
seems to be directly contrary to the annual statistics
of motor-vehicle accidents collected nationally, which
show a reduction in the rate of accidents as the regis-
tration has increased year by year. The opposing in-
dications of the two compilations are cal brought
out in the following tabulation:
4 ; Fatalities
Number of ,Motor-vehicle
Year Pa eis per 1,000
deaths registration venicles
[QSeeeeae eee. oss SS eee. A 7, 625 6, 146, 617 1, 23
OO Peo cha een ces cance sce saseceeee 7, 968 7, 565, 446 1,05
Che () ME SS tice ives eee eee 9, 103 9, 231, 941 . 99
GC eee ee RU bcos owe bee es oe 10, 168 10, 463, 295 97
te eR on Mele cna eee oe 11, 666 12, 238, 375 oth)
a eee eR en hoon eo Socineic oe sales 14, 412 15, 092, 177 . 96
LOCAL STATISTICS
. Accidents
: Number of |Motor-vchicle
State accidents | registration Der dee
IM alg ses ee a ee ee ee ees 135 69, 100 1,95
(ORCC ee Seeger 459 161, 739 2. 84
VI Sy 024 ONAN SiR i 2) 1,012 265, 541 3. 82
“ADGA ila a ap epee ae ee 1, 606 496, 380 3. 23
It is possible that the explanation of the difference is
that the annual statistics express the salutary results
of better traffic regulation, growing familiarity with the
motor vehicle, increased caution, and improvements in
the design of vehicles and highways; while the State or
local statistics, being for the same time and for approx-
imately equal states of advancement with respect to
the above factors, express the natural result of differ-
ences in traffic density. The probability that this
explanation is correct seems to be strengthened by an
examination of the particular causes of the accidents
29956—25|——2
0 100,000 200,000 300,000
WASHINGTON ........___- 265,541 1 ,
ORIEGO Neweeeres 6 ea (61,739 c—_eeeee
MONTANA _..-.._..-..... 69,100 _—<a«»n
Fic. 2.—Motor-vehiele registration, July 1, 1924
as classified in Table 6, from which it appears that the
principal cause contributing to the inerease in the
accident rate is the element of recklessness and care-
lessness, 8 human fault nor eradicated by regulation,
and not greatly affected by increase of knowledge, but
one which becomes more and more potent for disaster
as the traffic density increases.
CROWDED ROADS INCREASE ACCIDENT RISK
Considering the summary of the State statistics for
the months of December, 1923, and January, April,
May, June, July, August, and September, 1924, which
are given in Table 1, it is to be remembered that the
States represented are among the sparsely settled areas
of the West. Yet even in this section it will be observed
the accident rate is 3.23 per 1,000 vehicles over an
eight-month period. Conservatively estimated for a
year the rate becomes 4.5 accidents per 1,000 vehicles.
In other words, the average driver in these States has
1 chance in 222 every year to mect with an accident.
Assuming the span of driving years over an average
lifetime to be 30, the conclusion is that in the Pacitic
Northwest one driver in every seven is liable to accident
during a lifetime of driving. And for the driver who
travels the more congested highways the risk 1s con-
siderably greater.
PER CENT
0 5 10 IS 20
DE 1a ' ’ ‘ '
JA BG es
ra ARES
4 —_—_——
J TS
J Bs A
Ta AO
8 = oa a eS
Fic. 3.—Total number of accidents in Montana, Oregon, and Washington, by months
TABLE 1.—General summary of motor-vehicle accident data
State
Total
Mon: | gio Washing-
tana | Oregon ton
Nimiberiofeeeidents:--.....---.-.--.- 135 459 1,012 1, 606
Motor-vehicle registration !._..-...__- 69,100 | 161, 739 265, 541 496, 380
Number of accidents per 1,000 vehicles. 1.95 2. 84 3. 81 3. 23
Number of fatalities. .----..-.-------- 33 | 56 104 193
Ratio of fatalities to accidents (per
GUO) ae ee ee eee 24.4 12,2 10, 3 12.0
Number of fatalities per 10,000 motor
SIE Le (5c enna acre oe ia Cc. 4.78 3. 46 3,92 | 3. 89
Number of persons injured - -- 168 448 THOS: 1, 651
Ratio of persons injured to ac ;
(ee Cot) ee, a ee 124. 4 97.6 102. 2 102.8
Number of persons injured per 10,000 .
MMOUOEA VEC MNC OS amram: > peer eie 24.3 Plath 39. 0 Bone
Number of vehicles damaged --.-.-_--| 103 386 932 1,421
Ratio of vehicles damaged to acci- |
Gemisuipel Comb mee -ste sooo. - ose 76u2) | 84. 1 92. 1 88. 4
Vehicles damaged per 10,000 motor oso
SHOTS. see can 14.9 23.9 Bol) | 28. 6
INCAS ONO ROR MSH 2 Se a cee a) 64, 732 45, 475 45, 816 156, 023
Motor vehicles per mile of roads--_--- lt 3. 6 5.8 . 3. 2
Population, 1920 census....----.------ 548, 889 | 783,389 | 1,356, 621 2, 688, 899
Persons per motor vehicle__.--_------ th 4.8 5.1 Ome
|
1 Registration for first six months of 1924 as reported in PUBLIC ROADS, vol. 5, No,
7, September, 1924.
Fic. 4——Number of cities in three States with population over 2,500
The influence of congestion is suggested by the
summarized statistics and by Figures 1 and 2, which
show that the frequency of accidents becomes in-
creasingly greater as the number of motor vehicles
increases. ‘The suggestion is strengthened by Figure
3, which shows that the greatest number of accidents
occurs in the months of July, August, and September,
when the roads bear the heaviest traffic, although a
comparison of these data with traffic estimates over
the entire year seems to indicate that the number of
PER CENT
(¢) 10 20 30 40
BYAWE TIENT coc gece ss wow Be ccy ,
UOUINTEII@IVING pete eect yc. Soh eees coacs 4tl
CRUSHED: ROCK OR GRAVEL..----- 14.3
BARMAN, ......2) 2: . ee, 26 om
Fic. 5.—Percentage of the total number of accidents in the three States on various
types of road
accidents per 1,000 motor cars is greater during the
winter months. The previous conclusion may also be
inferred from Figure 4, in which it is shown that the
number of accidents per 1,000 vehicles increases with
the number of cities over 2,500 population. And this
inference is again confirmed by the data presented in
Figure 5, which show that the greatest number of
accidents occurs on paved roads, which, radiating
from the more populous centers or serving as the main
trans-state traffic lanes, carry the densest traffic.
TIME OF ACCIDENTS
A number of studies have been made to determine
whether the accident risk is greater during the day or
the night. Table 2 is a summary of the findings over
the eight months’ period. While these figures are
interesting, the study has not been sufficiently detailed
to be conclusive.
TaBLeE 2.—E ffect of time of day on causation of accidents
Motor-vehicle accidents
Se Total
State Daylight Darkness Unknown
Num-| Per |Num-| Per |Num-| Per |Num-| Per
ber cent ber cent ber cent ber cent
MiGniAnas.....-.58s...- 61 45. 2 61 | 45.2 13 9.6 135 | 100.0
(Onn) 20 eee eee 241) 5255 al | BviGe8 47 | 10.2 459 | 100.0
Washington. ..__.---.-- 540 | 53.4 384 | 37.9 88 | 8.7) 1,012) 100.0
‘Rotel eae 842} 52.4 616 | 38.4 148 9.2 1,606 | 100.0
As shown in Figure 6, the greatest number of accidents
occurs during the day, but it is probable that the great-
est accident risk is after dark. Figure 7 illustrates the
relative amounts of night and day traffic upon the high-
PER CENT
0 10 20 30 40 50
DANIEIGHT Sy 0 occ ccee ese csses i I i ey a
DARKNESS a i a i i
WIIKINOWIN «2... ec. oe asecace ee 9.2
Fic. 6.—Time of accidents in the three States
ways in Oregon during May, 1922, as computed from a
traffic census made by the State highway department.'
1 This figure is confirmed very closely by the results shown in ‘‘A Report of Traffic
on State Highways and County Roads in California, 1922,” by the U. S. Bureau of
Public Roads and California Highway Commission with the cooperation of 24 Cali-
fornia counties.
10
PER CENT
0 20 40 60
DAYLIGHT._..... A
Db oc -
Fic. 7.—Relation of observed day and night traffic in Oregon, May, 1922
Using this information in connection with the present
data, Figure 8 has been computed, showing that 2.76
times as many motor vehicles were in accidents after
dark as in the daylight. It appears therefore that
although the greater number of accidents occurs during
ANIC IGH IT tee. cscs seceseereeal
ARKINESS 2... -o eee.
Fic. 8.—Relative number of accidents per motor vehicle in day and night
the day it is probable that the ratio of accidents to the
number of motor vehicles on the road is greater at night.
In Figure 3 the summer season is shown as the time of
the year during which the greatest number of accidents
occurs. It is possible that the greatest number of acci-
dents per 1,000 motor vehicles on the road may occur
in the winter months, but no traffic counts are available
to confirm this. If 6 per cent of the total annual traffic
occurred in December and 15 per cent in July, the acci-
dent frequency would be greater during December.? It
is noticeable from newspaper accounts that the acci-
dents in the Pacific Coast States become frequent at the
PER CENT
MOTORS VERIGIESIEBAVIESEROAD arson eee
COLLISION.~ TWO MOTOR VEHICLES oo. cae
MISGREWANEOUS sees. aes cee, eee
COLLISION-MOTOR VEHICLE AND OTHER VEHICLE... |.
Fic. 9.—Nature of motor-vehicle accidents in the three States, in percentage of total
number of accidents
beginning of the rainy season. This may be due to
lowered visibility caused by lack of sunlight, to rain or
fog in the atmosphere and on the windshield, to use of
side curtains, and to skidding, especially on wet or frosty
bituminous pavements. A more detailed study will be
required to determine during what months the greatest
accident risk occurs.
NATURE OF ACCIDENTS
Table 3 and Figure 9 give a summary of the nature
of the accidents in the three States over the eight
months’ period.
TaBLE 3.—Nature of accidents
State
= a = Total
Nuatire onaeutent Montana Oregon Washington
Num-| Per |Num-| Per |;Num-; Per |Num-| Per
ber cent | ber | cent ber | cent | ber | cent
Motor vehicle leaves
0): \6| ee ee 73 | 64.1 222 | 48.4 470 | 46.3 765 47.6
Collision of two motor
vehicleso = 3-6 nouns 31) 28.0) -164 | 35.7 341 | 33.7 536 33. 4
Equestrian or pedes-
trian run down_.__..- 8 5.9 31 6.8 120! 11.9 159 9.9
Collision of motor ve- 2
hicle and train..__.__- 150 ellie 23 5.0 25 2.5 63 3.9
Miscellaneous. ......... si) 3.7 6 1.3 30 3.0 41 2.6
Collision of motor ve-
hicle and other ve-
in Ae a 1 elt 8 Wed 14 1.4 23 1.4
Uinkmowmne=..--...-22.- 2 5B) 5 eek 12 1,2 19 | 1.2
Motgeece 2 s..-224 135 | 100.0 459 | 100.0 1,012 | 100.0 | 1, 606 ; 100.0
2 This is a conservative estimate, which is confirmed by the results of the California
report and the ‘‘Connecticut Highway Transportation Survey,’’ PuBLIC Roaps,
vol. 5, No. 1, March, 1924.
iE
The classification ‘‘motor vehicle leaves road,”
means that no collision occurred, although a machine
may have swerved from a road to avoid a smash-up
or have plunged from the traveled way because of
reckless driving, inexperience, intoxication, etc.
LOCATION OF ACCIDENTS
Due to lack of information in the newspaper accounts
the location of the accident in more than one-half of
the cases is classified as unknown. ‘The balance of
the data shown in Table 4 and Figure 10. should be
representative, however, of actual conditions.
TaBLE 4.—Location of accidents
State
a aS Total
lccatianiotiaceident Montana Oregon | Washington
— ae a =f lb
Num-' Per |Num-| Per |Num-| Per |Num-| Per
ber cent ber cent ber cent ber cent
Winksmowiles.2-..-<=..-- 74 54. 8 248 54. 0 640 63. 2 962 59. 8
Omicunvere...--<0---2-< es dle al 48} 10.5 103 10. 2 166 10.3
Onigraden....-..-.0---- ie 12.6 42 9. 2 80 7.9 139 Bi
On straightaway-_-.-..-- i Gh @ 47 | 10.2 i 7.6 131 8.2
Intersection of highways 3) «62.2 30 6,5 | 50: 4.9 83 §. 2
Railroad grade crossing. 14: 10.4 28; 6.1 30 SO) 7 4.5
Onmibridges- 2 ---.- 25. 5 3.7 16 3.0 sonore 53 ah &
MOtalecsc2cccneees 135 | 100.0 459 | 100.0 | 1,012 | 100.0 | 1,606 | 100.0
Contrary to other published data the greatest
number of accidents in this section occurs on curves,
and the next largest number on grades, which may be
on acurve or a straightaway. The number of accidents
on the tangents occupies third place. The mountain-
ous character of the country in these three States and
the consequent large number of curves may account for
the greater number of accidents on the curves. It is
conceivable that in the Middle West the greatest
number would occur on the straightaways. The grand
total curved length of roadway in the State compared
with the grand total straightaway length must be an
important factor in determining where the greatest
number of accidents will occur.
TABLE 6.—Summary of the causes of accidents
KIND OF ROAD SURFACE IN RELATION TO NUMBER OF ACCIDENTS
What bearing does the type of road have upon the
accident rate? This is an important question to
which engineers are in need of an answer. ‘able 5
and Figures 5 and 11 show that the greatest number
of accidents occurs on avements, which represent only
1.9 per cent of the rural road mileage of the three States.
But this does not mean that pavements are the most
dangerous types per se, but that the paved roads are
more crowded due to their location near populous
centers or on main State arteries, and roma to the
higher speed made possible by these types of roads.
An attempt was made to determine whether the cement
concrete or bituminous pavements were the more dan-
gerous, but was abandoned because of lack of sufficient
data to support any positive conclusion. The percent-
age of accidents attributed to skidding was much higher
on the bituminous pavements, but the number of acci-
dents per mile of pavement of each type seems to be
practically the same. The crowded condition of the
road and speed and recklessness seem to be the chief
causes of the accidents, and the increased risk due to a
slippery pavement seems to be minimized by additional
caution on the part of the drivers.
TaBie 5.—Number of accidents in relation to type of road surface
1
|
State |
a __ ee ae Total
Kind of road surface Montana Oregon Washington |
Num Per |Num-! Per Num- Per |Num- Per
ber | cent ber | eent , ber ; cent ; ber | cent
——s 1 a ' = ‘
| I i {
Unknown....- 98)| 72i6! aed 27-0) 437 | 4eh2e e.G5Gn 4nd
Bavement. 22.5222 25--- | 8 5.9 267 Sone ve aOUnI eons 675 | 42.0
Crushed stone or gravel.| 22) 1633): 57, 12.4; 151 14.9 230 14.3
15 ai apeiron E ee; eb Mp 2 | 241 Bd. 4 95
Weiee. ...----2-2 135 | 100.0 459 | 100.0 | 1,012 100.0 | 1,606 | 100.0
The causes of accidents are given in summary form
in Table 6 and graphically in Figures 12 and 13. The
causes are subdivided into faults of persons, equip-
ment, and highway design.
Montana Oregon | Washington Total
Z a , — | ae
Rate per Rate per | Rate per Rate per
Number 1,000 Number 1,000 | Number 1,000 |Number| 1,000
vehicles vehicles vehicles . vehicles
oe ee ee | = | = oes ae
Faulty operation by driver: ;
Tee MC ORG Ura LN GRU OS pene eee nce onc en eee ee ewan saree eee ese ce2ni|fcca=a-een|~sesescese-o|acessemeas |p --~---2% 2a 3 0.01 | 3 0.01
Incompetence and inexperience - .. 2 0. 03 5 0.03 8 5 03 | 16 | . 03
(Clanlkslice: al nh GG), SRE SRE Gr eRe ee EO OREN ay iy eee re ee 1 Slip 5 | . 02 6 01
Operation by intoxicated persons. 4 . 06 il SG 26° .10 | 41 - 08
Excessive speed.._.....------- eh ots 34 21 43. 65 98 . . 20
Recklessness and carelessness - 36 woe 197 1,22 478 | 1. 80 71 1 1.43
Violation of traffic laws.-..-.- 3 . 04 18 aitil | 71 227 | 92 .19
ieee Man INGO IGE eine. I etme ne cs See eweee cee 3 . 04 8 05 . 43 16 54 mld
ill caten) |e <I ee RRR 2 en oh cmc ee Soa eas See 69 1. 00 274 1.70 , 677 2.55 1, 020 2. 06
Faults of others than driver:
(Cea ce) RUNS SIC OISIS LOG lee ee ese ge ee a 1 -O1 6 . 04 24 +09 _ . 06
We deeiieimiallentoug Velen iOMway....-.-04--.-.-.2--5-. 52-552 22--neo ren afee- secon sc [sesioe ese eee 1 Ol , 5 . 02 "| 01
WML ere USE 9 OTE cy SM ll og 19 28 48 - 30 87 280 154 | oul
Pee nanEn c emmenet: Si: x... ..caaeeae-.--------- 3 20 . 29 55 34 | 116 44 191 38
4 | —= : + ———
Fauity equipment: : = igh -
Roowonimpropenlyradiusted brakese:..........-----..--------------------- 3 . 04 3 02 © Ly 047 ve a
Gieimcate mgt heme 8 2 es cic os\ccie cs = SRR SRE: Se Soe St eee = 3 . 04 20 : HE 23 . 09 6 we
Drivingwwithioniyonedight.........--..-.------ See eee nent ier awe oe 1 01 3 02 | il | eeee ee a - ue
TDicagehter [a ORE ELT eee I eee eee a eee a ee ee Pee eee 6 . 04 - . 2 : . 02
[epee VOM IMe NO MOMUUON COTS 2... 6-2 cee nccce cer ce cop cescecccceec|oe sess eee |b ett Se elec ae sce] eee + ae ae ara a ota ‘a
Taye Gye ore TUS] wiyoy0 150 CC SE ee ee ee eee ol OY a a a am 4
Nie@namieal URERI OWS Me __.. oe. cee -- oo seme oo cages neon onc ece ee -ee eens 21 ae) 24 atl) : 5 ui
BA MUS ee ee a nearer 1; OU ee ee ee ;
cece ae ee el 29 | 42 57 135 95 . 36 181 | __ 36
12
TasiE 6.—Summary of the causes of accidents—Continued
, : - ™ Montana Oregon Washington Total
— Rate per Rate per Rate per Rate per
Number 1,000 Number 3,000 Number 1,000 Number 1,000
vehicles vehicles vehicles vehicles
Faulty highway ama ; ‘
Md Tap MIG Cd ae i oes ee oe caeeemame rs ll lenses = --| A)... 2-2.
tie li “ i se ee 2 0. 03 8 0. 05 9 0. 03 19 0. 03
Narrow bridge or i Se ee ee ao - Ol : Ce -O1
¢ ate, irregular, or i HOGI SU OASeeeee oo ec ce ence dee e eens US. conc ac owes oe ee eee ee ee = Seer ete ee fea n anes oe
Et emia sine) iin slime 8 Bt) 51 , 32 91 34 150 730
Theo lac teuneaplWil.. ee oo oe eee oe ee ees Peers eee ec oe 1 WQI. ocnccccocleeessece see), | an -
Winhagsssaly ols rueton Ol viCWl--.------ 2s seereneee esa see sees ae aoe 1 .O1 2 a {Oil a) . 02 8 . 02
IiGlemomde pnesslomsiimi Me bwWaie =- <2 2-4. = 2 Sate ee = er ee ree ee eee 2 mol 4 . 02 6 .O1
VICTOR OPI ON Stee ac. pee - yy = ci ne seme eee oe ee eae aoc e ee 6 . 09 7 . 04 12 . 05 5 . 05
ROCA sce... ate. a. See. See . . 5 ee | ily/ . 25 73 . 45 124 47 214 . 43
—— | 69 1.00 a74 1. 69 677 285 | 1,020 | 2. 06
PaulivienerameonubvaciMiwen. =... -.. cm ee see Se ee eee eee = aC 7 . 377 , ; B
Faults of others than drivers___-- Phe DS 2 A eS Flies os Bae tee 20 . 29 55 . 34 116 . 44 191 38
‘Penalit yaecruiomventt me... oe a oe ee ee ccs Sea wise a eee meena 29 . 42 57 35 95 . 36 18h . 36
Welty Me hway GenUiniOlSes:=—2.-......222cceeesco-- 4 = Se ooo ee eee Ne 25 We . 45 124 wad 214 . 43
(Gennaio tial? xeso. « saie oni epee eae eels ee ee ra eee 135 12) 459 2. 84 1, 012 OMe 1, 606 3. 23
TABLE 7.—Detailed analysis of accidents in Montana
. 1923 1924 Total
eae January | April May June July | August son ot Number | Per cent
PREDH aT] UerrCO) PIKE GIOL SNA s no meee eee ees See eee eS ee em ees 14 3 14 13 19 14 38 18 135 100, 0
Results:
INinimmbeti@ Gifeiialiite see cian) aoe eee ee Sale ae 3 3 2 1 5 4 12 3 33 24,4
INAbbaoll ore Oe TOTALS Wali OLATO ee = Soe a oe me eer te 17 3 16 17 30 20 42 16 168 124. 4
Number of motor vehicles damaged_...-.--------------------- 14 2 Il al 15 ll 25 14 103 (lay, 7
Time: ————s ——=== —— —
Dagteliths 22 ee acca ee ee eee ee a ee ee ee 5) 3 9 8 i) 8 14 5 61 45, 2
Tara OS ee eee - S aohoeenccssce ape eer ee Roe EC ee if 2 5 5 9 6 16 il 61 45, 2
TWD O Mates. epee eee econ) Pee eee yen oee 2) eee eee eee V0 Eee seee 8 2 13 2.6
tile. ..:-.. 2... a Se eee Sesser 14 § 14 13 19 14 38 18 135 100. 0
Nature of accident: ——a en | ‘ -
Collision of two! motommeliginme----.- 9 ee 2 ee. 3. |_ oe. 3a 3 3 7 3 | 8 4 31 23. 0
Collision of motor veliclonwamimothor Velie! @sssees seme. =e sete (p= see |e — = meee een | eee Ue ere ee = || Ames a|| Seren one 1 off
Collision oimoton velicloemclithain: 222-24 ses= esse se eso eee 5 1 ls eee bere are 1 6 1 15 WAL, al
Motor vehicle leaves road__.........-.-.---------------- eerste 4 1 9 9 9 s) 21 | iil 73 54.1
eq uestiian orpedesubiaiy WOME OW Nis ess sss 252.5 e eee IL 2 (IUieRes er erence = 2 | Bereer ees 7 Pe A 8 5.9
IMUSCeILANEOWSE . - =. 5.2 oe ees in oe SS nee | eee ae dl oes ae be eS Pe eeery| eae 1 2 5 3.7
UMEMOWille..o-.------ =e SS Te Ln SE ae, 2 eer an ae 1 |_----.----|----------)---=------|---------- (PS epecesccirs eyes eee ore eee P 1.5
PTO tel ease. =. <3 = Shae Srey re eee eee Seer em 14 5 14 13 19 14 38 18 135 100. 0
Location: ae i oil
TAIMOAGMENACGLONOSSING 88 cae a oe en ee ee eee 4 il leliseeeneen-|. eee 1 6 1 14 10. 4
TMEGT SEC HIOM! Of TMBINW AY Se nia sic cose crs oS aren <yare eeeene ors eeere et (ne 1 erate eae et esl ell Ree Pit eae ee ee 3 2.2
ON :StRaT eb aye ee oo ee = ee i) 1 econ ees Poe eee eee Sores ee ee re 7 5. 2
On CUigWeNe Sees. aes anite 2 Ses 2 cel 2 i Beeersee 3 1 1 4 3 15 Nib Tl
OMe Ra Co Siss s hae ys See ee ee el Ee ae 3) 3 2 2 6 1 iy 12. 6
OmprialGe.... = S2ee= = = cee maa aloe ea sata cee re re es | 1 25. a 2) ee cree 2) | eee 5 3.7
IDMOW T)...- eee. SRE ees ee ee oe! 2 8 § 16 10 18 13 74 54.8
AINOUOIE. . .....cigaee on acese se casscees aaa5 esc 14 14 13 19 14 38 18 13h 100. 0
Kind of road surface: a ile : ="
HARUN. seoec— oo ose edn eee cone ee go see eee ee eee | Se | rene | elena 1 1 1 3 1 i 6.2
Macadam, gravel, or crushed rock.....-...---......-- Sess Dee eee ees a | conse eee 2 10 6 3 22 16.3
IBENGMNOT bie a.m Re Se wh mn nn |) | 2) Soceaeee 2 1 1 2) s 5.9
WMRRTOWATE = 22 ERS ee ee ce ED 13 5 12 12 14 2 28 - 2 98 72.6
"TCI no = Reta IN << ee 20 14 5 14 13 19 14 33 18 135 100. 0
CAUSES i ; =;
Faulty operation by driver:
Imcomipetoncesamd inex penienGos. -. -- auemmee 55 Se eeerme ey ee | ener | nea 0 A ea eS ae ee PE (BT a 52 |S. ae 2 ee)
Operationioy ntoxicareaeensmnss. —-22- - 502-2 o-oo eel ee seers ee 2 2) | eee | SCA eis a ee |e 4 3.0
JSC OSSIN C/SCOG cette «aii 1 1 1 5 9 1 2 1 21 15.6
Recklessmess ancdcarciessmess = oasecee- a. nese ese cee enone 10 2 60) Ee eee eee 1 13 5 36 26.8
Violation of tramigiaw .......2-2sceeeesee= so seen] = ae mee | eye ee ae |e ae | 2 AR See See 3 2.2
Miscellaneous. - ....<s.... SSeS eee ee... Se | ee cee he 2 oe eer eee 2 ee eee |e 3 P49
ON eee ee oe ae ee il 3 10 ra 9 6 alee, 6 69 Ses
Faults of others than driver: °
CInildimums empaseno ad. - =. See = = cence - gee 2 ee i | a ere ee |e 1h) ae eee ] ai
BV Disee Rae cheer meee ee ya Cod Dy pilates | eee 1 ik 8 6 19 14.1
i i a ee cee 2 ij ae | ei, 1 1 9 6 20 14.8
Faulty equipment: [.
Poor or improperly adiustedshimkes. ...... .........-----_...-.|_ 229 ee | |p ee a, IA ol Ci. as 3 2a
Glanimegem@cllia tee seen. occ 2na essence oe eee eee ee 1 ae i ie eee Wane eee 1 3 ono
Drrineathwonlyomewignte. 2 ee cee len a ere | (fe I | See ete es ie ee i st
Miveheigalibreakdowtee — seen: ooo c 0. cue eee on ele o 1 33 3 4 4 1 5 21 15.6
Miieeellemeclion.... .-. -ooec seinen oe ee eo a see ree | ea | reer reece ee reg |e | (1 eases eee 1 eth
iC ee. ee ee re 1 1 3 4 § 4 5 6 29 21.4
Faulty highway conditions: = ‘ |
Nannongliie hay. es 5 See wo SS aoe sen eae =o es a ee 1s || eee re ee ae Dy |e ios pe 2 iL. 8
Unnegessaryenhatniac tion! Of VOW oes. 20 os coag aces eco nee elle ee Seen | =e ee | Ih | Baeeereees 1 alt
ELOGNORY SUbCiS (7 a nr sane nine CRM | el ello weseallnn eyccene 2 3 3a | Beale & £9
NitiemeNpiting tsi: ..-.. - mm see oo es escent ee ee ere 1 il D5 25 |e ane 6 | 4.4
cio). ee ee me. |... ME) ca 1 2 4 3 jee 17 | 12.5
SUMMARY OF CAUSES . . .
Faultyioperabtion by7drinewe —. 22. see ces u cou eceeceees 11 3 10 7 9 6 17 6 69 fl 3}
anal tsvo fet hersiihianudrivere.. ......0....-.2------cee-o--- une cle. 2 10) ere eres | ee err 1 il 9 6 20 14.8
Hipaal Gaymengg peng ene 2s Soumh a 1 1 3 4 5 4 5 6 29 21.4
Faulty highway cen ditiongae se. . a eee Soe eee... |e | ee 1 2 4 3 Hale lee 1255
Ginandittaleeseer:.... ci: Rene yen 14 5 14 13 19 14 38 18 135 100. 0
13
TABLE 8.—Detailed analysis of accidents in Oregon
INjmmibemohaccidemtsss ce... cc a... cece s. -- ceeee ee eaeeceeee.
Results:
Nittmiber ofifietalities:.......-.--.-..---. 2-2. a enue -e ae
Numberioi personsiinjumede-..-........-..-.-.--2---.-2s------
Number of motor vehicles damaged
Time:
TN os SRE SOC Eee a 2
Nature of accident:
Collisvon, of wo motonvehicleste..o.2<-.....-.---.-----------
Collision of motor vehicle with other vehicle........_.._..___-
Collision of moter vehicle amd train..................-....----
Miotomvelaicieilervies NO@d =.= .0-.--.-.-- 5222-2 eee
Equestrian or pedestrian run down. ._............--.-.--..---
ANI Eeeee en WG rem myye soe en eae cce cease
Urreeincnvyn eee eee ee. oo oe k ec eme ence ceccen !
Location: ;
Railnoad gnade crossing... ...........---.----- enon ne cence nnene
Imperseetionvet higitways..........-.--.---2--2--2c-c-s-eee-eee
(COMPBUNAIGMILAWIAW so =aa east ce aca see oes cee enw ocacueancseee
OTe UTR Omen Serene been te te eo eee eee |
(Oia) AUC, Ae a © Bs ee ee oe ae ME
Ome nie: So ere Meee se ces ek es
(Uiesric ieee =e Os ae re eee
Kind of road surface:
De eNOS So te Ss eee Saale geese eae.
Macadam, gravel, or crushed rock_....._.-....-----.---------
PEN GTI 11 ene te 5 ee So oa oo odie wee ce wee ees
WUDU SOV e Rae hes SS eS ee
CAUSES
Faulty operation by driver:
Incompetence and inexperience.._.._.......-..--.--..--------
Choilieliera Clakvens <a re een ep ene
Operation by intoxicated persons___._.._...._..--------------
TB SRURISUN() TSIOVEVE (61, SUMMER
Recwlessmessmandicareléssmess..........-.---cec-----ue--ecee
WiCleInOnmotetne itt Cul weeee ees 2 eens one
MINSialllame oll seo ae) en Sc oe mee
Fauits of others than driver:
Ciquillal abn BiHRORS ntCHICl ya5 9. 4S eee eee
Pedestrian fails to give right of way.__.......-.-.-.----------
IMBC CIMROUSHEES oc wccconcteuceusecccesss Be ec oes
Faulty equipment:
CO aver vivayeg Tiny) 5151 1] 6 = mc age een 2 ge a
Diva SowALNeOMinnOMmenltte...--.--20--eaceceeceeoeesecese
IDA bales eAhelOOVElls iesalliS 8 eee oe eon ne a ae
Lack of nonskid appliances
Poor or improperly adjusted brakes.._..........-.------------| ---e-eeeeeceeecceee eel eeceeee eee eee ee ene |
MieeiamicaltbregkdOwns...- 25... 22-2 cn coe e ee eee cee eee cass
Faulty highway conditions:
ISICON: | AEE 5 pj a rr
ING ENO mena Secor CUNO toc .. an nnsnccecne cone caceecuceencsceee
ILaolke coy feqbe ccd bc aa ee
Unnecessary obstruction of view.______...._-_..-_-.-----.----
Holesior depressions in highway-.................--....-.-....
RIUGIEGUIMA COR eon hacen ceo es oe ek ae cenecceeese cesta
I IRSGGIENICO USMS 22.08 Rete en Soe ceca uacektecceescccee
SUMMARY OF CAUSES
Henliy operationvby driver. .........--..-----.-s.--------+----snc-
HAMIES OL OblWerS tiem OrlVCl.....-22.2 cece eee ese secs ceececeececee
TE (UWE? CEO TOD VON NOT=) 0) egy ee ep nn
Hamlbyemiphwway CONdItIONS- ............-.-.-------+=---<------6--
Gar ee ee I. cece eae bee biueedes ye
1923 ' 1924 Total
Decem- | : lg
mene | January | April May June July August os) sim ' Number | Per cent
=.) 2S | —, |
41 | 39 37 7 65 45 101 73 58 459 | 100. 0
21 3 | 10 | 10 6 8 15 2 56 12.2
40 | 45 29 61 56 93 70 54 448 | 97. fi
| 42 | 44 34 | 48 360 78 62 42 386 84. 1
| — ——- == =—= == aa [SS Ses = = = SS moe cio =
17 25 24 32 | 25 48 35 35 241 52.5
Opp | 13 12 32 | 16 37 26 ie 171 | 37.3
5 1 1 i% 4 16 | 12 10- 47 , 10.2
41 | 39 37 65 45 101 73 5S 459 | 100. 0
ity 14! igi 25 i 34 34 | 15 | 164 | 35.7
ee I le ees 2, 1 my 1} 8 ig
3 3 | 3 6 i I a 5 23 5.0
15 | 18 16 33 24 | 54 31 ail | 995 7 48. 4
5 | 3 2 1} 5 Tl 5 3 31 6.8
mpm. Nae, MI. Se | 1 2 1 2: 6 ie
il, Uae a | ee. te 6 il
41 39 am 65 45 | 101 3 58 | 459 100.0
ay 4, ae 5 2 ae 1 5 28 | 6.1
om 21 3 | 3] 3! 4 G3 4 30 | 6.5
12 ® | 4° 1} BARe ee J 3 6, 5. 47 | 10,2
5 3 Bee 10 ' 6 | 11 5 8 48 | 10.5
4 9 | a 5 4 9. 7 9 42 9.2
Bee is! By | 4 ‘ae oe 4 S) 5 eae 16) 3.5
12 19 19. 31 28 67 45 27 248 | 54.0
_— == |~—— =e | a,
41° 39 | 7 65 | 45 | 101 Ta 58, 459 , 100. 0
\ SS , ma === = aS Oe ee
Le 2 ieee 1 t 4 (ee wi 2.4
3) [Coens 7 9 6 20 4 va 57 12. 4
25 | 39 21 41 24 52 35 30 267 | 58.2
77 |S ‘om 14 14 | 25 29 26 124 97.0
4) | 39 37 | 65 45 101 rey 58 459 | 100. 0
el ' ——— = = = = | —~-_
| | | | |
Baca eee ese. ee ee |, eee, 5 | itil
Ses) eee Weave eeecc-n|essceonnss Te eee ieee! |S See eee = 2 No Je Ly nr
1 oe 2 2 1 1 1 i 13 J 2.4
ae oe il 4 7 4) 10 4 34 | 7.4
21 iy 15 27 15 , 45 34 28 197 43,0
3 Da sca ae Ae ea care eee ee: 2 18 | 3.9
Pt: 3) ia a oe Rae 2 2 ebiallliageyp i, SEES os 8 1.7
32 | 18. 19 39 25 60 46 | 35 | 274 59.7
SSS = = — — ve = ae |s aS \ a aE SS
| ! | l
Me ae a Nee aes EE 1 1 1 6 Wee
ee eae et ee ee Ca ee. ee | cere iL! BD
il i 8 | fa 5, 14 8 4 | 48 10.6
1 3! 9 | i 5 | 15 10 5 55 | 121
eee H — at =a aa = al — = was owas == | = = ——
. eetaiees eee 1| il) 1 31 a
5 2) | fh fig ae 3 3 2 4 20 | 4.4
Bo... Aa bg fs ley 8 Daye a oage e, 3) ni
1 6 | 1.3
1 aw
24 | 6.2
57 | 12.5
_ = a
Be tain en: cae ile erieeeeee Ss Lt i, re 1 8 id
Se je a i, ine Nee S . oe See ates 2 4
ee amnanan RE 2. a eg ao oye oC anne,” || erie een 1 a
Be Oe aac aes aioe e | Sete ee siaee sarge eee Wl ib | 2 .4
B icieshs icine So 1 ine eee TS ST ie } om 4
cna 14 | 4 12 4 iB 9 | 3 By iL 3
feice si Sool a ee 1: 3 2 ly, Sa tausie 3) 7 | 1.5
Pe 14 | 7 15 8 1 11 6 73 15.7
| --f == o— ss ae = as = = <= = as=
32 18 | 19 39 | 25 60 | 46 35 274 59. 7
1 34 Q 7 5 15 10 5 55 iat
8 4 2 4 pe 14 6 12 57 | 12.5
eee 14 | 7 15 8 12 11 6 TP 15.7
| = pam! a = MJ eet col — a 2
41 | 39 oc 65 45 101 783 58 | 459 100. 0
| |
14
TaBLE 9.—Detailed analysis of accidents in Washington
Nima nOtAeGICeMtse.. .. ae eee cece tees se ensaseeeee
Results:
foam bet Of fae aes oc ee on ce ea ae eee
Nwniber of persomsvinjuned__.._....-.--.---.-..-.-++----+------
Number of motor vehicles damaged.__....-_..----------------
Time:
1Oy NC Ea ee ne ee et ee ae a Lapeer
Nature of accident:
Collisionratitiwo motor vehicles... ..22522---- - dee --- -- soe eee
Collision of motor-welieletand train.......-.-..--------..---<.
Miotorveliiele leavestraad a. ...---..-..---------- ome ee cneee
EKauestrianvor pedestrian run down.....-.--.--------6--------
Miliseeliameows..-- 98 aa eee oc cckcccsees Sane See
OLGREN TOIT SS, 2p ce eo vo, ae ere
TAMER remecpcerserecns: < maga tee a Ser ee ee ent eee
Location:
Repilfoad’eradetorossimg. ... .-. -. 2. ee. ee 3 --
IntenseetionsofehighWays_-........-. 22.2222. c20e- 222 eee cee
OnaStnaleibawaye.. 0-25-2005 nce ets ee sece oaceoe sae
(OMMGUIIEV Es —. < © a tere aoe ee ie eee ai >...
Ontprad Gh Os eee ty ee ae ne Ni De ee
@mabridte: - ee eee oe 8 ee ee Be ee
sail’ < oc) a Yee mc at ee SA an nap Gene ns PER ine ee ne Eee So Bune Ny
ONGC cS. <= Se ees a ae creer
Kind of road surface:
1) £ ee O y
Macadam, gravel, or crushed rock._..........-.-...-...---.--
Le 1S1iz 1 o£ i le ean dR hm oT a eee. 1
(Wimibnigiyaiie ie << 3c ae eet ee rn er Cre eer
CAUSES
Faulty operation by driver:
Lenonancerohtramicirmlesiaee. 2... _ pose oreo ene eee eee
Incompetence and inexperience....._......-...-.-.-----.------
Childrontdnivensea.2 222 See Ls aoe eee ae ee ee
Operation by intoxicated persons__......_-.--..-.------------
BSGRSBIVGISCCG—...2es.. MM 2 ooo eee ae
Recklessness and carelessness. ..._........--.-----------------
Wiclamoniomtraticldwse ieee... 2... ue ee eee ene e eames
Faults of others than driver:
@Nciilkel eibhoky FO TOS 110)\6 |e ee are ee eee
Pedestrian fails to give right of way__...-.-.-...-...-..-------
Miscellaneous
Faulty highway conditions:
Lack of sight distance
Narrow highway
Holes or depressions in highway
Skiddy surface
Miscellaneous
SUMMARY OF CAUSES
JOSHMNE NSE Comore eng Canal JNK CODA) e 5 eee ome ete es ee eee
Faults of others than driver
1923 1924 Total
— | January | April May June July August A onal Number. Per cent
69 55 44 152 ' 128 194 215 | 155 1,012 100. 0
8 7 12 12 24 11 17 | 13 104 | 10.3
75 36 92 158 196 159 187 132 1, 035 102. 2
67 57 103 111 146 147 | 168 | 133 932 | 92. 1
32 27 28 39 70 106 109 79 540 | 53.4
31 23 16 54 47 75 78 60 384 37.9
6 72: ae 9 11 13 28 16 88 8.7
69 55 44 152 128 194 215 155 1, 012 100. 0
25 17 16 45 41 64 73 60 341 | 33.7
iG |_. amen eee i 3 2 3 | 4 14 1.4
1 1 1 6 2 5 4 | 5 25 2.5
30 25 | 17 68 62 99 105 64 470 46.3
9 11 10 B 15 17 18 17 120 11.9
eee | eee 3 5 7 10 4 30 3.0
STi i no cates ee G8 lene’: i Se I a 2 1 12 ine
69 | 55 44 152 128 194 215 155 1,012 100. 0
D 1 1 9 2 5 5 5 30 3.0
5 2 3 8 6 6 | 9 ll 50 | 4.9
12 4 4 8 2 14 17 16 77 7.6
10 2 2 13 12 27 24 13 103 10.2
8 9 3 6 12 15 18 9 80 7.9
ee B | agen 5 2 10 10 2 32 3.2
32 34 31 103 92 117 132 99 640 63.2
69 55 44 152 128 194 215 155 1, 012 100. 0
1 see ee |e ey 2 7 9 4 24 2.4
4 3 3 24 14 48 33 22 151 14.9
18 41 20 41 35 86 85 74 400 39.5
46 1 21 86 77 53 88 55 437 43, 2
69 55 44 152 128 194 215 155 1,012 100.0
= : a ————— mae =|
du cea cc chee oss Lees. eee OM MSS 23. 20 ae eel a ee 3 .3
Ot eas oc... | en Ue eh Sa cae 8 nf
boc on eegel eae on alll oo oe eee Sees eon | aha ee ee 5 5 5
3 1 Buleemeeee 6 8 5 i. 26 | 2.6
| eee: 4 8 7 8 6 H 43 4.2
41 19 16 65 63 97 102 75 478 47.1
10 4 2 12 is 19 9 8 71 7.0
oe) ae 1 1 1 7 26 6 1 43 4.3
59 25 28 86 97 158 128 96 677 | 66,8
ea 2 2 3 2 2 1 12 24 | 2.4
1 1 1) |e 2 OUR ee 5 15
4 4 6 27 Cn | cee 24 16 87 | 8.5
5 7 9 30 10 2 25 28 116 11.4
10 1.0
23 Be
1 al
6 .6
1 oil
31 31h
23 Ph &
95 9.5
=!
ee ren 1 lesacce veal: seen coeee Beeeeeeee eas os eae ns Seen 1
Sap sc a a | naan eee Rgeee tue 3) 9
2256s el es HPS 0). = 0 aa 1
Cee. Lol. oi Beedl.. aoc deel: 2 Conan oe an meee see 1
ea... eee ee aa 2 1 1ko. 2 see 1s 5
Ms. 28 | ee oe | ee ee ee 4 | F
‘oe SR ie 1 6 10 14 32 17 91 | 9.
es 1 Seeteeee 4 1 1 57. aoe 12 it
— 17 3 13 12 21 37 | 21 124 | 12.
i | =
59 25 | 28 86 97 158 | 128 96 | 677 66.8
5 7: 9 30 10 ay 25 28 116 11.4
5 6 | 4 23 | 9 13 25 10. 95 9.5
oe 17 | 3 31 | 12 21 37 21 124 128
69 55 | 44 152 128 194 215 155 1, 012 100. 0
15
HIGHWAY SPEED ZONES SUGGESTED
Making the highways safe for the general public
should be one of the chief functions of the highway
engineer in the vate icing of improved motor trans-
a The whole problem of regulation has hitherto
een too generally regarded as a function of the police
authorities, rather than as an engineering and economic
problem, the end of which is the provision of safe and
adequate highway transportation. Since the appear-
ance of the motor vehicle, public opinion and the con-
sequent attitude of government toward its use have
PER CENT
5 0 20 40 60
UN OM Nees awe enene ene NERS
ONMCURVIE. 2255)...
oh GRAD EHS. .00......2.5.
N STRAIGHTAWAY
INTERSECTION OF HIGHWAYS.
ga GRADE CROSSING
Fic. 10.—Loeation of accidents in percentage of the total number
passed through two stages. In the first stage, corre-
sponding to the period when motor vehicles were few
in number and there was abundant room for them on
the roads, they were regarded as a’ life-menacing
luxury, and inflexible and unnecessarily low maximum
speed limits were rigidly enforced. In the second
stage, which coincides with the increase in motor-
vehicle registration to large proportions, the roads
have become crowded and at the same time there has
been a softening of the rigors of speed regulation,
largely the result of growing confidence in the motor
vehicle and the overcoming of the fears and jealousies
which it inspired in the early days.
PER CENT
80
BAIR Eee see ea OMT
CRUSHED ROCK OR GRAVEL -.-.---13.2 s_—_—<,
AVIEII ENN es cmon wm ee 19e
Fic. 11.—Classification of roads, by type, in the three States
It may now be timely to suggest that this liberalizing
tendency, desirable as it is in the interest of free trans-
portation, has proceeded ‘not wisely but too well.”’
Whereas it is certainly essential to impose no more
severe restrictions on the operation of vehicles than
may be absolutely necessary, it is also important that
liberality be kept within the bounds of safety.
The statistics presented in this article clearly indicate
that the greater risk exists on crowded highways. It
PER CENT
0 26) 40
RECKLESSNESS AND CARELESSNESS 44.2 :z.Iznssnssnmmmnsssnasesan
eomine Fe | “43-3 ==
EXGESSIVESSPEEDEE _...... wee 6.| —_——
VIOLATION OF TRAFFIC LAWS. E. 2°5 =
EGHANICAL BREAKDOWNS... ee 4.0
BARINGSHEADEIGRTS. ........-...--....--....--..... 2.9 2
INMOXIGATIONE =... 2.
Fic. 12.—Chief causes of accidents in the three States, in percentage of the total
number
follows therefore that on such highways there is need
of greater care in operation and the adoption of what-
ever measures may lend themselves to the reduction
of the seriousness of unavoidable accidents. While
the prevention of recklessness, as already suggested,
is difficult of attainment short of the elimination of the
reckless driver—and how many are not at times reck-
less—the reduction of speed on congested roads will
go far to prevent the occurrence of the more serious
accidents.
Ultimately there will be need undoubtedly for a
reduction of congestion by provision of more extensive
highway facilities. The part the highway engineer may
play in this solution is illustrated by the proposed grade
separation and superhighway now planned from Detroit
to Pontiac, Mich. The Washington State Highway
Department is also preparing to reduce the traffic
PER CENT
0 20 40 60
Y OPERATION BY DRIVER.........63.58 . .
FAULTS Pees THAN DRIVER... C|.2 cree
FAULTY EQUIPMENT... |. 3 me
FAULTY HIGHWAY CONDITIONS. 4.0 =
Fic. 13.—Summary of the causes of accidents in the three States, in percentage of
the total number
density between Seattle and Tacoma by the construc-
tion of two 18-foot parallel pavements separated by a
parking space, all built over an entirely new route.
Each side of the road will be used by trafhe moving
in one direction only. But such engineering solutions
of the problem will take some time to accomplish, and
there is need of 1mmediate relief.
It is believed that the establishment of speed zones,
in each of which the maximum speed limit will be
determined by the congestion of traffic in the zone, will
in some measure provide an immediate remedy. Such
a plan is now in effect in Maryland, apparently with
favorable results.
CRUSHED-STONE TESTS AND THEIR RELATION TO
pest VICEVOF Tilt FINISHED PAVEMENT
By A. T. GOLDBECK, Chief Division of Tests, Bureau of Public Roads
specifications 1s toward definiteness with respect
to every item involved. Materials are described
in as much detail as our knowledge seems to warrant.
It has been found that much contention on the part of
the engineer, the contractor, and the materials producer
is saved when each one knows definitely what is ex-
pected of him. Specifications for materials involve a
description of the materials in terms of specific quali-
ties which those materials possess in order to be satis-
factory for the particular type of construction con-
templated and it is generally the case that where there
is much deviation from the specifications, unsatisfac-
tory results are likely to occur.
In general, there are two properties which crushed
stone must possess for its successful application to any
We TREN D in the writing of present-day highway
particular type of road construction: (1) It must be
crushed to the proper size, and (2) it must have physical
qualities which make for enduring construction.
Crushed stone was first used to a considerable extent
in the building of the macadam type of road in the
days of steel-tired traffic. As early as 1878 the first
physical test was developed in the French School of
Bridges and Roads, primarily as a test of the suita-
bility of stone for waterbound macadam construction.
Later the Dorry test for hardness of rock was likewise
developed in France, again primarily to determine the
suitability of rock for waterbound macadam. In this
country other tests were developed by the late Logan
Waller Page in the then Office of Public Roads, United
States Department of Agriculture. These tests were
the Page impact test for determining the toughness of
16
rock, the cementing value test to determine the binding
value of rock dust, and the absorption test. Lately
a new test has been developed, but not perfected, the
so-called accelerated soundness test for rock.
PHYSICAL TESTS FOR ROCK
The Deval abrasion test—The Deval abrasion test
is made by placing a sample of 50 pieces of uniform-
sized stone in a cylinder inclined at an axis. As the
cylinder is revolved the pieces of rock and particularly
their corners are worn to dust, and the amount of wear
is expressed in percentage of the original sample. The
French coefficient of wear equals 40 divided by the
percentage of wear. Both terms are used and should
not be confused.
The Dorry hardness test—In the Dorry hardness test
a cylinder of rock is held against a revolving disk upon
which dry crushed quartz is fed, and the amount of
wear is determined.
The toughness test—In the toughness test a 1-inch
cylinder of rock is subjected to the impact of a hammer
falling from an increasing height on a round-ended
plunger resting on the specimen. The toughness of the
rock is expressed in terms of the height of fall of the
hammer when failure takes place.
Cementing value test.—In the cementing value test
the rock is ground to powder and mixed with water in
a ball mill, then compressed into a cylinder, which is
dried in an oven and finally broken in a special impact
machine, whose hammer falls from a constant height of
1 centimeter until the specimen fails. The number of
blows required to produce failure indicates the relative
cementing value of the rock.
The absorption test.—The absorption test consists
simply of determining the amount of water a rock will
absorb in a given time.
All of these tests were designed in the days of water-
bound macadam, and they have been criticized as being
unsuitable in their application to our present-day uses
of rock in Portland cement concrete, bituminous
macadam, and bituminous concrete pavements sub-
jected to rubber-tired traffic. A discussion of this
point will not be amiss at this time. In the days of
waterbound macadam and steel tires the rock was
subjected to surface abrasion by vehicles, which
created a considerable amount of dust, and also to
internal wear, due to the grinding of one rock on an-
other. The dust created served to bind the road to-
gether, the dust of some rocks possessing this property
more than others.
This was the sole reason for the development of the
cementing value test. At the present time it has prac-
tically no significance for we can no longer depend on
the cementing value of the dust to hold the road
together. Under rubber-tired traffic very little dust is
formed by abrasion and this is rapidly dissipated.
There is little excuse then for the cementing value test
in present-day specifications for crushed rock.
n bituminous macadam of the penetration type the
action of rubber-tired traffic still produces internal
wear particularly of the stone not covered with bitu-
minous material. There is still need therefore for some
kind of abrasion test such as the Deval test. In the
bituminous concrete type of pavement the surface
stone is still subjected to forces of high intensity such
as impact from high-speed traffic and the action of tire
chains and it is likewise our belief that there is the
possibility of considerable internal wear when the stone
is too soft. It will be seen theroforo that there is still
need for tests to determine the strength of the rock.
The Deval test and the toughness test both accomplish
this purpose.
In concrete pavements the stone is surrounded by
Portland cement mortar, which prevents any move-
ment and which offers considerable protection. The
stone is subjected only to the abrasive action of traffic
and to a slight extent to the disintegrating influence of
the weather. It has been found both in service and
by means of specially conducted tests that when the
stone in a concrete pavement is so soft that it wears
faster than the mortar, uneven and rapid wear results,
especially where tire chains are used. We need have
no fear of abrasive wear from rubber-tired traffic
alone. Some of these old-fashioned tests then, such as
the cementing value test and Dorry hardness test, no
longer have any particular significance when applied
to crushed stone as now used in highway construction.
ABRASION AND TOUGHNESS TESTS STILL VALUABLE
On the other hand, since stone under present-day
traffic conditions must still possess strength, durability,
and resistance to abrasion the tests which measure
these properties are still applicable. The Deval abra-
sion test and the toughness test for rock still have high
value, though undoubtedly they might be improved
upon. It is for the above reasons that highway speci-
fications for rock still contain clauses which require a
specified maximum percentage of wear or a certain
minimum toughness. The toughness test has been
largely supplanted by the more simple Deval test in
many laboratories, for it has been found in general
that the Deval test serves every purpose. It is a
toughness test and an abrasion test combined. Some
specifications further safeguard the quality of the rock
through the use of both the toughness and the Deval
test.
I have mentioned two other tests, the absorption and
the soundness tests. The absorption test measures
the amount of water which is absorbed by the rock.
Ordinarily rocks which have a high absorption are
soft and are not apt to withstand constant repetition
of frost action. The accelerated soundness test is a
test which is designed to simulate the destructive
action of repeated freezing and thawing. As at
present performed the rock is immersed in a saturated
solution of sodium sulphate for 20 hours, dried for
4 hours in an oven, and this treatment repeated five
times. Rocks which are not durable under frost
action will disintegrate or crack under this test.
Sodium sulphate crystallizes in the pores of the rock,
gradually expanding and destroying the structure
much after the action of ice. The indications are
that the test is too severe. A rock which fails in the
test will not necessarily fail in service, but apparently
the test does detect rocks which are likely to fail under
service,
TEST LIMITS FOR VARIOUS TYPES OF CONSTRUCTION
Problems in economics are involved in the use of
materials and for this reason specifications for materials
to be used in similar types of construction differ in
different States. In some localities it is advisable to
use material which in other States is regarded as in-
ferior, for ultimate economy results even though the
road does not possess the highest lasting qualities.
Crushed stone is now used for the most part in macadam
‘Ws
construction which will later receive a surface treat-
ment of bituminous material, in bituminous macadam,
in bituminous concrete, and Portland cement conercte
pavements.
Generally where waterbound macadam is built, to
be later surface-treated, heavy traffic is not expected.
Here good practice would not as a rule allow stone
with a percentage of wear of more than 6. Economy
may demand, however, that a softer stone be used in
certain localities. For bituminous macadam a per-
centage of wear of more than 6 should not be used;
for bituminous concrete, which ordinarily is of a
more expensive type laid on a more expensive base
than bituminous macadam, the percentage of wear
should not be more than 5, and in order to reduce the
liability of the stone to fracture, an additional require-
ment for toughness is used, the value for toughness
being set at not less than 6. Instances are known
where disintegration of bituminous concrete seems to
have resulted from the use of too soft a stone. Many
engineers specify a lower percentage of wear for trap
or granite than for limestone for a given type of con-
struction. The reason for this is that trap and granite
are naturally more resistant than limestone, so that
granite, showing a percentage of wear greater than
normal for that type, is likely to be partially disin-
tegrated or of otherwise inferior quality even though
the actual wear as shown by the tests is the same as the
limestone. In connection with waterbound macadam
construction certain types of rock, such as quartzite,
eneiss, and schist, generally can not be used success-
fully, due to the difficulty of binding such materials.
In order to study the physical properties of stone
desirable for concrete road construction, the Bureau of
Public Roads has conducted a rather elaborate test
in which 62 different kinds of concrete containing
imported aggregates were subjected to the abrasive
wear of a special rubber-tired vehicle operated at 20
miles an hour. The vehicle was guided by means of
a track so that the wheels ran continuously in the
same track. In this way the test was accelerated.
The vehicle was first equipped merely with solid tires,
and after running it for thousands of trips it was con-
cluded that, so far as rubber-tired traffic alone is
concerned, the present wear on concrete roads is not
an important factor in limiting the life of the road.
In many sections of the country, however, there are
conditions which make for abrasive wear, such as the
use of tire chains, and grooves have been worn in
concrete pavements due to this cause. The test
vehicle was therefore equipped with tire chains and
the test repeated and soon the surface wear became
very appreciable. This test has been described in
detail in Pusric Roaps, and the important points
brought out were:
That rubber-tired traffic alone produces no appreciable
wear on a concrete pavement.
That tires equipped with tire chains cause appreciable
wear. This wear is practically independent of the hard-
ness or type of coarse aggregate so long as the coarse
aggregate has at least the same resistance to wear as the
mortar. When softer aggregates than these are used, the
wear of the pavement increases as the stone becomes
softer. So far as can be determined the percentage of
wear in the Deval abrasion test, which results in equal
wear in both stone and mortar, is approximately 7.0.
From the standpoint of abrasive wear alone there seems
to have been little choice in this test between crushed
stoneand gravel. It should be emphasized, however, that
abrasive wear is but one of several factors which should
influence the choice of an aggregate. The question of
structural strength of the concrete, relative liability to
cracking, and subsequent spalling and consequently high
maintenance expense must also be considered. It ap-
pears from these tests that notwithstanding the fact that
the Deval abrasion test was originally designed for
macadam road construction it seems to have considerable
significance for the specification of rock for conerete road
construction.
USE OF SCREENINGS AS FINE AGGREGATE
While discussing the question of physical properties
of coarse aggregate for concrete roads, it will be well
to consider the use of stone screenings as a fine agere-
gate in concrete. In general stone screenings are char-
acterized by the presence of an excessively large amount
of dust and an excessively large amount of very coarse
particles with a corresponding lack of particles of inter-
mediate size when compared with the grading of good
concrete sand. One of the tests for the suitability of
fine aggregate for use in concrete is the so-called
strength-ratio test in which the tensile strength of 1:3
mortar briquets is compared with the tensile strength
of Ottawa sand mortar briquets of the same proportions
made at the same time. The ordinary assumption is
that when these strengths are equal the sand is an
excellent concrete material and in general this holds
true. When this test is made with stone screenings,
it is almost invariably found that the briquets made
with the screenings test higher than Ottawa sand
briquets, but notwithstanding this fact, it is generally
true that concrete made with stone screenings as the
fine aggregate has a lower strength than concrete in
which sand is used. It is also true that in many cases
where stone screenings have been used the concrete has
not been resistant to the weather. Particular trouble
has been had with limestone screenings, and no doubt
this is because the concrete has been lacking in density,
due to the poor grading of the screenings. If it were
possible for crushed-stone producers to turn out
screenings with the same mechanical grading as a good
erade of concrete sand there would be no question of
its suitability for use
UNIFORMITY OF CONCRETE
The technical literature of late has placed emphasis
on the question of uniformity of concrete. Concrete
structures, including highways, are proportioned on the
assumption that the concrete has a definite assumed
strength. Thousands of concrete cores have been
drilled from concrete roads, and the results in many
cases show a great lack of uniformity in the concrete,
the crushing strength in some cases varying as much as
100 per cent on the same job. It is not sufficient that
the concrete shall have an average strength equal to
that for which the structure was proportioned when it
is so much weaker than that in many spots. It is
highly important that everything possible be done to
bring about uniformity of strength. Already several
of the State highway departments have begun to take
measures aiming at more uniform concrete. lowa is
now carefully weighing both sand and stone entering
into concrete road construction. Other States although
still measuring by volume, are taking into account the
fact that the volume of sand may vary 25 per cent due
to variable moisture content. Devices are beginning
to appear which aim not only to insure more exact
measurement of the fine and coarse aggregate, but also
of the water used for mixing, which is another of the
decided variables which result in lack of uniformity.
18
There are few engineers who realize the part the
coarse aggregate plays in influencing the water con-
tent in a concrete mixture and the strength of the re-
sulting concrete. Whenever the gradation of the
coarse aggregate changes during the progress of the
work, this necessitates changes in the amount of water
required to produce a given consistency of concrete.
To illustrate the effect of gradation on consistency,
tests were made on 1: 2:3 concrete, using both hmestone
and gravel as the coarse aggregate. The results are
indicated in Table 1. It will be observed that changes
in the gradation of the coarse aggregated produced a
marked effect on the workability. For instance, a
certain amount of water produced a slump of 3 inches
when a 44 to 2 inch normally graded aggregate was
used, whereas exactly the same quantity of water pro-
duced a slump of 6 inches when the material between
the 14 and 1 inch screens was removed. On the other
hand, by maintaining a constant consistency, which of
course should be the aim of every mixer operator, fully
14 gallon less of water per bag of cement was required
when the stone was graded from 1 to 2 inches than when
normally graded from 14 to 2 inches. In a 6-bag
batch this would mean a change of 3 gallons in the
measured water content and of course a correspondingly
large difference in strength.
TaBLe 1.—Resulis of tests of consistency of 1: 2:8 concrete,
varying the size of aggregate and amount of mixing water
Crushed stone Gravel
lL a8 Water re- Slump Water re- Slump
Grading! _ quired per when a quired per when a
BEEEGE HLS bag of ce- constant bag of ce- constant
ment fora | amountof | ment fora | amount of
given con- water is given con- water is
sistency used sistency used
Gallons Inches Gallons Inches
8.0 1 4.5 Ps
77 2 4.4 3
ae 3 4.1 3
Ga) 4 3.9 6
6.8 6 3.8 if
Producers of stone can aid in the movement for
more uniform concrete by maintaining an absolutely
uniform product during the progress of the work.
This is an ideal which at the present time is not being
generally attained. No doubt it is due in part to the
present custom of screening aggregates at the pro-
ducing plant and then more or less inefficiently mixing
the various sizes together in a car before shipment.
Possibly if more accurate methods were used in com-
bining the screened sizes the desired results would be
obtained. One possible solution for obtaining more
uniformly graded coarse aggregate is that of shipping
the screened sizes separately to the central proportion-
ing plant, stock-piling them there and later combining
them in the desired proportions. It is recognized,
however, as one of the difficulties in this proposal that
ordinarily it is hard to find sufficient space to stock-
pile separate sizes, and of course additional time is
required to measure the sizes separately at the pro-
portioning plant.
SIZE REQUIREMENTS
In addition to quality requirements for crushed stone,
specifications call for grading of the stone in a par-
ticular manner for specific types of construction.
Unfortunately engineers in different States have
different conceptions of what constitutes a proper size
of material for the same kind of work, and this of course
leads to needless expense in the producing plant which
is called upon to supply materials to several adjacent
States. It would be highly economical if a definite
standard of sizes could be set up which might be
followed by the users of crushed stone. The road
materials committee of the American Society for Test-
ing Materials is now at work on the development of
such a standard. The standard of sizes proposed by
this committee which is designed to meet the require-
ments of the various types of constructions now used is
given in Table 2.
Tasie 2.—Mazimum permissible range in mechanical analysis of
stone for nominal sizes as proposed by the road materials com-
mitice of the American Society for Testing Materials
Percentage by weight passing various sizes of laboratory screens
Desig- | 2 eee
nated |
size A “4% | % 1 14% 14% 2 | 244 3 34%
inch | inch | inch | inch | inches| inches} inches' inches| inches) inches
= - = 3 ee
een Per Per Per Per Per Per Per Per
Inches |Per cent) cent cent cent cent cent cent cent cent cent
0-4! | 85-100! 10m. oa... 8 ieeo= ant eee a | i | ee
0-141 15-75 | 95-100 C00 ear eee [ee Soe wis Soe ee
0-341 17s) ees 95-100. LOOM 5.52 s|-ceenee (bosses |ooe eee sees Sees
My- 0-15 ; 95~100 HOO! nw «cage eiulaee oe flees |e |e
Yy-34 0-15 | 25-75 | 95-100) a0), Sener ee ee eae Ee Smicieyerocoasa
Yy-1Yy (Oxi |; same 40-75 |..-.---; 95-100 WOOr ac sen al Seeoca2 2s eee |e
14-2 0-5 5=20) (sae 40 =i meee eee |e ar 95-100 100 S52. Se eee
Yy-24 0-6)" |Peeeens NOP soe AQevan|os occ osleeeee es 95-100 ‘100 Saeeeee
Y-1 0 0-15 | 25-75 | 95-100) 3G) Perse eiers|toccicase Rmeree ese - |cooccs
A | eee el occa O-15 | Qh75 Maee100\ “100 eect cedlcg ek eee
VOY Nc cn ans [paces ae ee re ee i Onl on Semmens 25-75 | 95-100 NO Greate
PA LY eH eae ere: oe NW De ec fe Soke Eoeeee len eccse 0-15 | 25-75 | 95-100
|
! Designated sizes 0-14, 0-14, and 0-34 when used as screenings in waterbound
macadam road construction shall conform to the following additional requirement:
Passing 100-mesh sieve, 6 to 12 per cent.
2 The lower limit for designated size 2144-3814 may be changed to 2 inches when neces-
sary to utilize the product of a crushed producing designated size 4-2 inches. The
upper limit for designated size 244-314 may be changed to 4 inches in the case of very
soft stone or light or porous slag.
It will be observed that the sizes are stated in terms
of laboratory screens. This procedure is followed
rather than that of stating the size in terms of the size
of the commercial revolving screens simply because
there are many factors in plant practice which affect
the size of the screened stone, whereas the laboratory
practice is standardized. It is the individual pro-
ducer’s problem to run his plant in such a manner that
the laboratory screen requirements will be met. There
is no doubt that the various laboratories will be glad to
work with producers to this end for procuring the de-
sired result.
The various sizes of crushed stone and crushed slag
recommended by the road materials committee as
shown in Table 2 are thought to be adapted for the fol-
lowing uses:
Intended use
Fine screenings for waterbound road construction.
Aggregate for fine-graded bituminous concrete.
Coarse screenings for waterbound macadam road construction or aggre-
gate for bituminous concrete.
»| Fine dustless screenings for bituminous road construction.
-84| Coarse dustless screenings for bituminous road construction; coarse aggre
gate for cement concrete where the maximum size is limited to 34 inch.
Coarse aggregate for coarse-graded bituminous concrete; coarse aggregate
for cement concrete where the maximum size is limited to 14 inches.
Coarse aggregate for cement concrete pavements or other concrete struct-
ures where the maximum size is limited to 2 inches.
6; Coarse aggregate for cement concrete pavements or other concrete struc-
tures where the maximum size is limited to 2)4 inches; coarse aggregate
for bituminous concrete base.
Commercial 34-inch stone for bituminous road construction.
Commercial 1-inch stone for bituminous road construction; binder stone
for sheet asphalt, ete.
4) Coarse aggregate for bituminous macadam, penetration method, and bitu-
minous macadam base; wearing course for waterbound macadam.
Coarse aggregate for bituminous macadam base or base course for water-
bound macadam.
I)
REINFORCED CONCRETE PAVEMENT SURVEY
HIGHWAY RESEARCH BOARD REPORTS PROGRESS OF ITS STUDY
By C. A. HOGENTOGLER, Highway Research Board, Nationa! Research Council
HE STATUS of the survey for determining the
economic value of steel reinforcement in con-
crete pavements carried on by the highway
research board of the National Research Council is
such that the procurement of very definite information
on this much-discussed question seems assured. As in
every other research, it was necessary to have speci-
mens from which were eliminated all variables except
those whose effects were to be studied. Instead of
being especially constructed, as is ordinarily the case,
in this instance they had to be selected from the vast
mileage of plain and reinforced concrete roads which
has been constructed up to the present time. Since
the difficulties attendant upon the attempt to compare
a road of one type with another of a different type
were keenly appreciated, every effort was made to
procure for study only such roads as contained both
plain and reinforced sections. The seeking out of
such specimens has taken considerable time, since,
unfortunately for the purpose, roads are generally
either entirely plain or entirely reinforced.
It is now felt that the time and efforts spent in the
selection of the desired roads have been amply re-
warded, since they have been found in sufficient
number to warrant conclusive results. In addition to
such experimental service roads as the DeKalb, IIL,
and the Sacramento-Riverbank, Calif., surfaces, con-
structed in 1912; the Du Pont highway in Delaware,
constructed in 1915; the Milwaukee County, Wis.,
and the Los Alamos-Gaviota, Calif., roads, constructed
in 1917; and the Columbia Pike, Va., constructed in
1921, there have been located 188 highways whose
surfaces contain both plain and reinforced concrete
sections which were built at the same time, by the
same contractor, under the same supervision, and from
the same materials and have been subjected to the
same traffic and climatic conditions. Thus in these
roads all undesirable variables are climinated except
those of subgrade and strength of concrete, which are
common to all highway experiments. These highways
are distributed through 30 States, ranging from Con-
necticut to California and fron. Minnesota to Texas,
with one in Ontario, Canada. In three counties of
New York State alone, representing both good and
poor subgrade subjected to extreme frost action, there
are 304 sections containing reenforcement, of lengths
varying from 100 to 1,000 feet, with a total length of
over 200,000 lineal fect, each section being part of a
conerete road and having plain sections on cach side.
Contrasted with this soil condition is one found in
Mississippi, where, although frost is lacking, the soil
has an extremely high volumetric change. In this
location an experimental road 1 mile long, half of
which was reinforced, was constructed in 1915.
In addition to differences in subgrade conditions these
roads represent age, mix, traffic, and cross-section varia-
tions. In the reinforcement are included different
weights of mesh and various designs using bars.
The final road inspections are now in progress, and
will probably continue throughout the summer, after
which the data will be analyzed and a report of the
findings submitted. Analyses of subgrade samples
taken in connection with the investigation are being
made by the United States Bureau of Public Roads,
The University of Maryland is cooperating in the ex-
amination of cores for determination of the effect of
time and cracks on reinforcement; and various State
highway departments have offered cooperation in the
road inspections and core-drill work for checking loca-
tion of steel and thickness of slab.
20
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ROAD PUBLICATIONS OF BUREAU OF PUBLIC ROADS
Applicants are urgently requested to ask only for those publications in which they are
particularly interested. The Department can not undertake to supply complete sets
nor to send free more than one copy of any publciation to any one person. The editions
of some of the publications are necessarily limited, and when the Department’s free supply
is echausted and no funds are available for procuring additional copies, applicants are
referred to the Superintendent of Documents, Government Printing Office, this city, who
has them for sale at a nominal price, wnder the law of January 12, 1895. Those publica-
tions in this list, the Department supply of which is exhausted, can only be secured by
purchase from the Superintendent of Documents, who is not authorized to furnish pub-
lications free. ;
DEPARTMENT BULLETINS
No. 105. Progress Report of Experiments in Dust Prevention
and Road Preservation, 1913.
*136. Highway Bonds. 20c.
220. Road Models.
257. Progress Report of Experiments in Dust Prevention
and Road Preservation, 1914.
*314. Methods for the Examination of Bituminous Road
Materials. 10c.
*347. Methods for the Determination of the Physical
Properties of Road-Building Rock. 10c.
*370. ane Results of Physical Tests of Road-Building Rock.
15c.
386. Public Road Mileage and Revenues in the Middle
Atlantic States, 1914.
387. Public Road Mileage and Revenues in the Southern
States, 1914.
388. Public Road Mileage and Revenues in the New
England States, 1914.
390. Public Road Mileage in the United States, 1914. A
Summary.
*393. Economic Surveys of County Highway Improvement.
35¢.
407. Progress Reports of Experiments in Dust Prevention
and Road Preservation, 1915.
*463, Earth, Sand-Clay, and Gravel Roads. 15c.
*532. The Expansion and Contraction of Concrete and
Concrete Roads. 10c.
*537. The Results of Physical Tests of Road-Building Rock
in 1916, Including all Compression Tests. 5c.
*555, Standard Forms for Specifications, Tests, Reports,
and Methods of Sampling for Road Materials. 10c.
*583. Reports on Experimental Convict Road Camp, Ful-
ton County, Ga. 25c.
*586. Progress Reports of Experiments in Dust Prevention
and Road Preservation, 1916. 10c.
*660. Highway Cost Keeping. 10c.
670. The Results of Physical Tests of Road-Building Rock
in 1916 and 1917.
*691. Typical Specifications for Bituminous Road Mate-
rials. 10ce.
*704. Typical Specifications for Nonbituminous Road
Materials. 5c.
*724. Drainage Methods and Foundations for County
Roads. 20c.
*1077. Portland Cement Concrete Roads. 15c.
*1132. The Results of Physical Tests of Road-Building Rock
from 1916 to 1921, Inclusive. 10c.
No.
No.
1216. Tentative Standard Methods of Sampling and Test-
ing Highway Materials, adopted by the American
Association of State Highway Officials and ap-
proved by the Secretary of Agriculture for use in
connection with Federal-aid road construction.
1259. Standard Specifications for Steel Highway Bridges
adopted by the American Association of State High-
way Officials and approved by the Secretary of
Agriculture for use in connection with Federal-aid
road construction.
DEPARTMENT CIRCULAR
. 94. TNT as a Blasting Explosive.
FARMERS’ BULLETINS
. *3838. Macadam Roads. _ 5c.
*505. Benefits of Improved Roads. — 5c.
SEPARATE REPRINTS FROM THE YEARBOOK
. *727. Design of Public Roads. 5c.
*739. Federal Aid to Highways, 1917. 5c.
*849, Roads. 5c.
OFFICE OF PUBLIC ROADS BULLETIN
*45. Data for Use in Designing Culverts and Short-span
Bridges. (1918.) 15c.
OFFICE OF THE SECRETARY CIRCULARS
49. Motor Vehicle Registrations and Revenues, 1914.
59. Automobile Registrations, Licenses, and Revenues in
the United States, 1915.
63. State Highway Mileage and Expenditures to January
1, 1916.
*72. Width of Wagon Tires Recommended for Loads of
Varying Magnitude on Earth and Gravel Roads.
5¢
73. Automobile Registrations, Licenses, and Revenues in
the United States, 1916.
74. State Highway Mileage and Expenditures for the Cal-
endar Year 1916.
161. Rules and Regulations of the Secretary of Agriculture
for Carrying out the Federal Highway Act and
Amendments Thereto.
REPRINTS FROM THE JOURNAL OF AGRICULTURAL
Vol.
Vol.
Vol.
RESEARCH
5, No. 17, D-2. Effect of Controllable Variables Upon
the Penetration Test for Asphalts and
Asphalt Cements.
5, No. 20, D-4. Apparatus for Measuring the Wear of
Concrete Roads.
5, No. 24, D-6. A New Penetration Needle for Use in
Testing Bituminous Materials.
Vol. 10, No. 7, D-13. Toughness of Bituminous Aggregates.
Vol. 11, No. 10, D-15. Tests of a Large-Sized Reinforced-Con-
crete Slab Subjected to Eccentric Con-
centrated Loads.
* Department supply exhausted.
APPORTIONMENT OF FEDERAL
AID FUNDS AUTHORIZED TO BE
APPROPRIATED BY H.R. 4971
FOR THE FISCAL YEAR 1926
STATES
California
Colorado
Connecticut
Delaware
Florida
Georgia
Illinois
Indiana
Kentucky
Louisiana
Maine
Maryland
Massachusetts ....
Michigan
Minnesota
Mississippi
Missouri
Nebraska
AMOUNT
$1,541,870
1,056,171
1,264,164
2,472,636
1,373,237
474,801
365,625
892,878
1,983,089
936,927
3,191,479
1,938,693
2,070,396
2,074,360
1,411,607
997,262
685,140
635,783
1,090,118
2,225,227
2,124,151
1,291,960
2,417,727
1,548,473
1,581,969
STATES
Nevada
New Hampshire ...
New Jersey
New Mexico
North Carolina ....
North Dakota
Pennsylvania
Rhode Island
South Carolina ....
South Dakota
Tennessee
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Hawaii
AMOUNT
$948,076
365,625
935,082
1,185,166
3,657,096
1,699,168
1,180,699
2,789,588
1,755,105
1,179,668
3,360,123
365,625
1,052,549
1,215,020
1,622,985
4,415,715
846,467
365,625
1,449,713
1,118,987
797,295
1,873,308
934,947
365,625
73,125,000
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