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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.

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.

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.