America's Highways 1776–1976: A History of the Federal-Aid Program/Part 2/Chapter 8
and
Maintenance
In the late 1800’s, with the growth of the cities, the demand for better roads increased. The need to move farm produce from the fields to the city in a steady, dependable manner grew with the increasing city population. Yet, only about 150,000 miles of the rural roads were surfaced, while the vast majority was of rutted, packed earth that became unusable with inclement weather. In describing the prevalent condition of the roads in this country, General Roy Stone said, “In many parts of the United States the roads are torn up with the outcoming frost in the spring, soaked with autumn rains, frozen into ridges in winter, and buried in the dust in the summer, making four regular seasons of bad roads, besides innumerable brief ‘spells.’ ”[1]
Early grading operations were performed with pick, shovel, and animal-drawn equipment. This muledrawn slip scraper hauled very little earth compared to more modern devices.
Roadbuilding and maintenance, in the latter 19th century, was still primarily accomplished by the statute labor system using horsedrawn slip scrapers and teams and wagons. The road grader, first introduced in 1878, consisted of a steel blade hung beneath a wooden wagon. But changes were starting to take place. The Office of Road Inquiry, established in 1893, sent engineers to various parts of the country to construct object lesson roads in order to demonstrate that year-round good roads were possible and to show the proper roadbuilding methods to achieve them. In machinery, the steam shovel and steam roller were already in limited use but the new steam tractor, with its broad iron wheels, foreshadowed the retirement of the horse and mule from the road construction scene.
Grading a new location at a washout in 1914. At right a man uses a plow to form a ditch, others drive horsedrawn wheel scrapers.
Steam shovels were used for excavation work in the early 1900’s, but dump wagons were still horsedrawn. Bottom dump wagons, shown here, were especially useful for dumping heavy, sticky material.
1900 to 1916—The Beginning of Federal-Aid Construction
After the turn of the century, there were some very significant happenings which had quite an influence on the future of road construction. The Office of Public Roads (OPR) engineers continued to teach others how to build and maintain good roads under the object lesson roads program while also studying and investigating new methods themselves. The small Federal laboratory in the OPR developed tests for aggregates and other materials and made important contributions toward overcoming defects in early bituminous construction. Public Roads engineers determined and published typical specifications for highway construction, the first of which was in 1913 concerning the fabrication and erection of steel highway bridges.
With the coming of the automobile, the macadam and earth roads caused quite a dust nuisance in dry weather. However, it was also about this time that people realized that oil could be used as a road material. It was found that a road covered with oil would be free from dust in the dry season, yet hard and firm in the wet season. This led the way to early experiments with tar and bituminous material to improve road surfaces.[2] In 1905, coal tar and crude oil were experimentally applied to recompacted macadam streets in Jackson, Tennessee. After nearly a year of observation, it showed that the coal tar had penetrated from 1 to 2 inches and maintained a hard smooth surface. However, the light crude oil used showed little permanent results. The heavier crudes showed nearly the same results as coal tar. Late in 1906, coal tar was used by Khode Island on a short section of the New York to Boston trunk highway in Charlestown in much the same method as building an ordinary macadam road. After the subgrade had been thoroughly rolled, the number one stone (1¼-inch to 2¼-inch diameter) was spread to a depth of 6 inches and rolled to 4 inches. Heated tar was then sprinkled on the first course with dippers. The number two stone (1½-inch to 1¼-inch diameter) was next mixed by hand with hot tar and spread to a depth of 3 inches on the first course and rolled to 2 inches. A thin coat of fine stone (passing ½-inch ring) was then spread on the surface and rolled into the number two course to fill up the voids and provide a smooth surface—1¼ gallons of the tar per square yard were used in all. As this method provided a stable hard surface, it was advocated by State engineers for use on first class highways.[3]
Use of portland cement concrete pavement also was beginning to grow, as the steel drum tilting mixer came into use. The first rural concrete pavement, however, was not constructed until 1909 in Wayne County, Michigan.
In terms of new equipment and techniques, steel forms were being produced for concrete work and the gasoline engine came to construction work as the power unit for hoisting and excavation equipment, spelling doom for the steam engine. The diesel engine was also being developed and crawler tracks were being tried on tractors and cranes. A wooden-boomed excavator was rigged with a drag bucket in 1903, making this the forerunner of the drag-line. By 1907, a sheepsfoot roller was in use on embankment work on West Coast road construction. A rock crusher and elevator was mounted on a four-wheel truck in 1910 to become the first portable crushing and screening plant.[4]
First graders ever used on highway construction work. Fixed with adjustable blades to provide the desired slope and section, graders were suited for fine grading and shaping.
Even though the first Federal Aid Road Act was not passed until 1916, in 1912, the Congress authorized funds for the improvement of post roads with the appropriation of $500,000, to be expended in rebuilding and upgrading roads used in the rural free delivery of mails.
An early roller compacting a roadbed.
The first of these road projects to be built was in Lauderdale County, Alabama, where approximately 30 miles of road was graded and surfaced with gravel at a total cost of nearly $28,000. One-third of the cost was paid with Federal funds and the remainder with State funds. Under this post road program, each of the 48 States was to be allotted $10,000 and the remaining $20,000 was to be used for administrative expenses and contingencies. It was estimated that an average of $600 per mile would be spent on this improvement whereby about 50 miles would be completed by each State with their total joint fund of $30,000.[5]
The Office of Public Roads and the American Highway Association sponsored this road improvement in Dunn, N.C., in 1914, the first use of a drag in the county.
A horsedrawn sweeper cleans the surface of a macadam road in preparation for bitumen application. It rid the surface of dust and loose material so that the bitumen would form a positive bond between the cover aggregate and the macadam layer.
It is likely that these roads were built by contract, rather than statute labor as in the past, thus, recognizing the importance of the new road technology. However, though there was probably a change in the labor system, the roads must surely have been built by hand with pick and shovel and by horsedrawn slips and scrapers. The gravel surfacing material was no doubt hauled by teams and wagons. Though many new types of equipment were being developed or modified and improved, construction equipment advertising was in its infancy and so there was often a lack of widespread knowledge of the development. In other cases, if the equipment were known, often the contractors were not ready to accept it or could not afford it. Therefore, during this time, the older methods of road construction often prevailed long past the development of new machinery and techniques.
In this era of post road building, $1.8 million of State and Federal-aid funds was spent in the construction of 425 miles of roads—certainly not a very impressive accomplishment compared to present roadbuilding, but one that meant a great deal at the time. A further advantage of the 1912 Act was that the betterment of these post roads was a good training ground for the engineers of the Office of Public Roads, and this experience was to prove valuable in the administration of the Federal Aid Road Act of 1916.
Laying block pavement in Washington, D.C., in 1917.
1916 to 1926: The Start of the Federal-State Joint Highway Effort
Evidence of the success of the small previous Federal-aid program for post road construction surely contributed to the passing of the Federal Aid Road Act of 1916 which provided for the improvement of any rural road over which the mails were carried.
One of the central features of this Act, in terms of the future, was the requirement that the States must have a highway department capable of designing, constructing, and maintaining the designated roads in order to share in the appropriation. Immediately this brought about the creation of highway departments in those States not meeting this requirement. Other provisions of the Act gave the States the authority, subject to Federal approval, to select the roads to be improved and the nature of the improvement, plus the responsibility of supervising the construction and the obligation to maintain the completed projects.[6]
A steam roller provides motive power for a scarifier on an Indiana road in 1916. Scarifiers were used to loosen the material on the top layer of the road. The surface was then graded and compacted.
In the early 1900’s, some counties and cities hired full-time caretakers to perform the maintenance functions previously done by statute labor. This man was one of 95 caretakers for a Pennsylvania county who received $50 per month to maintain from 3 to 5 miles of road.
A Need for Maintenance
With Federal funds assured for highway construction, the door was open to considerable activity in roadbuilding. By 1918, a feeling of well being was the mood of the day. In the 1918 fiscal year alone, 6,249 miles of Federal-aid roads had been or were being surfaced.[7] New surface treatments were being utilized, and equipment technology was advancing to make work easier and more productive. However, the development of heavy trucks and their usage during World War I brought this mood quickly to an end. Roads that were suitable for travel by passenger cars rapidly deteriorated as they were subjected to the loads imposed by 5- and 10-ton trucks. Prevost Hubbard, the chief chemist and expert on bituminous pavements for BPR described the situation in Public Roads:
Hundreds of miles of roads failed under the heavy motor-truck traffic within a comparatively few weeks or months. Roads with bituminous surfaces, bituminous macadam roads, and bituminous concrete roads all failed alike, together with other types used in State and county work. These failures were not only sudden but complete, and almost overnight an excellent surface might become impassable. . . . A very large proportion of the failures have been characterized by an almost simultaneous destruction of the entire road structure, and not merely the disintegration of the wearing course or pavement proper.[8]
The Bureau of Public Roads conducted extensive research on this subject and concluded that possible solutions to this problem required: (1) Stronger road surfaces and better drainage, with special attention to sub-drainage, and (2) continual adequate maintenance.
The Bureau recommended during this same period that really economic and efficient maintenance could be secured only by: (1) Patrols assigned to definite sections for which they would be responsible for all ordinary routine work, and (2) well-equipped and organized gangs or crews continuously employed throughout the season to perform all work which could not be economically performed by the patrol alone.[9] These recommendations became the basis for the structure of most of the State maintenance organizations. 
A homemade tar kettle used to heat tar as a surfacing for dustless macadam.
The 1921 Federal Highway Act reinforced the construction and maintenance provisions of the 1916 Act by requiring the States to maintain the highway constructed under the program and specifying actions to be taken if this were not done. Section 14 of the Act required that where a State failed to maintain any road constructed as a Federal-aid highway project, the Secretary of Agriculture was to serve notice to that State. If the State did not repair the project within 90 days, the Secretary was to make the repairs by contract or Federal force account work and charge the cost against the Federal funds allotted to the State. No additional Federal-aid highway projects were to be approved for that State until the maintenance conditions were made satisfactory. When the Federal Government was reimbursed for the maintenance performed, the funds were paid into the Federal highway fund for reapportionment among all the States for the construction of roads. The Secretary could then approve further projects for that State.
Application of bitumen on a macadam road in 1912. The man in the center foreground is sprinkling aggregate onto the freshly poured surface. Today mechanized spreaders perform the same task.
Construction Partners
Unlike earlier roadbuilding procedures, such as statute labor or force account, by 1918, nearly all of the road construction work was done by contract. The State highway departments, after getting the approval from the BPK on their highway programs, project plans, specifications, and estimates of cost (PS&E), advertised for bids on the proposed work. After studying the bids received and selecting a contractor, a construction contract was awarded by the State highway department with the concurrence of the BPR. Copies of all contract documents, as well as plans and specifications, were forwarded to the BPR Washington office for review and analysis. This evaluation was to insure full compliance with Federal laws and regulations in order to avoid difficulties in paying the Federal share of the cost and to keep up with new materials and methods of construction developed by the various States. The information was passed on to the other States for their mutual benefit. All of the construction work was supervised and inspected by State engineers. Public roads field engineers made periodic inspections to assure compliance with the approved PS&E. All changes in the plans or extra work that became necessary during the life of contracts were reviewed by BPR. A final review and inspection of all engineering features of the completed project was made by BPR before payment of the final reimbursement for the Federal share of the work done.
This road was surfaced using the penetration method. Aggregate was spread on the roadbed first and the bitumen poured on top.
In the early twenties, the average length of Federal-aid projects was just over 5 miles, and the average cost per project was roughly $85,000. The average cost per mile was about $17,000. Of the roads completed during this period, about 25 percent were paved, and the rest were surfaced with gravel, sand-clay, or other select material. On the paved roads, about 65 percent was spent on surfacing, 20 percent on grading and nearly 15 percent on structures. The Federal share of these projects was approximately 50 percent.
The unit prices for the various items of road construction, such as excavation, concrete pavement and structural concrete, were, in general, more expensive in the twenties than they were in the thirties. Of course, this was partly due to the Depression of the 1930’s, but it was also due to the development of equipment to replace more expensive hand methods. This enabled roadbuilders to move more earth and pour more concrete for the same amount of money in the thirties than they could in the twenties.
The cost data were compiled on all projects and forwarded to the BPR Washington office for analysis to determine the trends in highway construction cost for various types of construction. This information has proven to be of such general interest through the years that it has become the basis of a quarterly index, showing the relative movement of highway construction costs over a period of years.[10]
During the early twenties, important advances and experiments were made in all phases of management techniques and standardization development in the construction and maintenance of roadways. This work by the BPR and private organizations increased the capability to produce cheaper, more efficient, quality roads.
A steam roller rolls a second coat of bitumen with chips on a macadam street in 1922. First a coat of bitumen was spread, then a layer of large stones, followed by another coat of bitumen, and, finally, a layer of smaller stones to fill in the voids.
By the 1920’s, crawler tractors were pulling scrapers and other equipment. This tractor could pull 5 scrapers at once, enabling these men to excavate and move material more efficiently.
An important program started by the BPR during this period was the “Production Cost Studies,” a management tool to promote efficient road construction operations. These studies on earth moving and concrete pavement construction produced practical applications. From the results of these studies, savings of from 25 to 35 percent were possible in earthwork by selecting the right number of appropriate pieces of equipment best suited to the particular job. The process applied to the concrete paving operations showed that production losses were mainly the result of the failure to provide appropriate hauling equipment in number and character to maintain the capacity of the concrete mixer. By careful elimination of such losses, astonishing increases of from 25 to 100 percent were made by Public Roads engineers in the output of working paving organizations. The most gratifying result, however, was the success that some contractors attained in nearly doubling their output by employing similar methods, and thereby permitting them to drastically reduce their next bids on concrete pavement items.[11]
Another important development in earthwork was the ability to compact soil embankments. Early experiments showed that the amount of moisture in soil had a great influence on the degree of compaction that could be attained. This, of course, led to the use of moisture control methods of compaction and the development of the “Proctor” method of testing the compaction of soil embankments, a method which later became standard on highway embankments throughout the country.
The Public Roads engineers were actively working with various State highway departments and universities in cooperative investigations to develop suitable cheap roadway surfacing materials. At the University of Georgia, tests were underway on sand-clay. In Iowa and South Dakota tests were being run on methods of stabilization of soils with cement and lime. South Carolina was experimenting with bituminous applications to preserve earth roads. Investigations continued in Iowa on the tractive resistance of various types of highway surfaces. In Kansas, tests were being conducted to measure tire wear on various surfaces. In addition, the Bureau also was continuously making routine examinations of highway materials and coordinating the work of a large number of State and commercial laboratories making tests for the acceptance of materials on Federal-aid projects. The result of this work was a general improvement of all laboratories with the corresponding benefit to both Federal-aid and State highway construction projects.[12]
A tractor-pulled grader maintaining a gravel-surfaced road in Minnesota. Self-propelled motor graders were introduced in the early 1920’s but were not widely used until much later.
A paving train near Memphis, Tenn., in 1929. Steel forms were set ahead of time on the subgrade to hold the concrete in place.
Excavation work on the Blue Ridge Parkway in 1936. In the background men drill holes for explosives used to break up rock, while a diesel-powered shovel loads earth into dump trucks.
The Swing to Power Equipment
Equipment for highway construction was undergoing some tremendous changes during the period 1916–26. The steam shovel was being replaced with gasoline engine-powered excavators. The lines of horsedrawn wagons were disappearing as dump trucks were taking their places. Crawler tractors pulling rotary scrapers were replacing horse or muledrawn fresnos and drag scrapers. Monstrous early models of the self-propelled scrapers were being developed in the early 1920’s.[13] A manual hoisting bulldozer blade was put on a crawler tractor in 1923, and by 1925 hydraulic controls were in use on the bulldozer blades.
The self-propelled motor grader was introduced in the early 1920’s, but it did not get widespread use until much later. By 1922, an all-welded tractor drawn scraper with a 6-cubic yard capacity was in use and by 1924 electric handsaws were put to use in construction. The steam crusher was being replaced with gasoline engine models with revolving screens and belt conveyors, and in 1923 a completely portable crushing and screening plant was placed on the market.[14]
Paving equipment was also coming into more use. In 1919, a bituminous distributor was introduced to help improve the quality and uniformity of penetration asphalt pavements; 1920 brought batching plants (volumetric) for concrete aggregates, eliminating a large amount of hand shovel and wheelbarrow work. In 1923, a traveling concrete mixer was introduced on pavement projects. An old issue of Engineering News-Record contains a detailed description of the construction of a concrete pavement in 1918:
The rough grading was done entirely by machine: meaning a pull-type grader equipped with a scarifier. Fine grading was done by hand. A concrete mixer rode between wooden forms, with volumetric proportioning of the mix. The concrete was struck off and tamped with an iron-shod wooden templet, finished with a wood float and a coarse wire stable broom. The concrete gang (23 men) averaged 500 feet of 9-foot wide, 8-inch thick pavement per 9-hour day.[15]
1926 to 1944—Building More and Better Roads
The Federal-aid system of building roads was well established by this time. Construction followed the same basic procedure with the State highway departments selecting, designing and constructing their own projects by contract, all with the approval of the Bureau of Public Roads and with partial funding from Federal appropriations.
The 1930’s witnessed an important advance—the introduction of the diesel engine on tractors. This diesel-powered tractor teamed with a 5-cubic yard capacity scraper moved approximately 16,000 yards of earth in 14 days.
Pressure from the general public was increasing to “get the farmer out of the mud”; and the consolidated school system required the improvement of many miles of roads in order to facilitate the busing of more children to the wider dispersed schools. To get more miles improved with the funds available, many of the highways were built as “stage” construction so that the road could be brought up to a higher type later with additional improvement as traffic volumes grew and the weight and speed of vehicles increased. Stage construction was also used for other reasons. Some road projects were let to contract for the grading work alone, or perhaps the drainage work and grading work, leaving the surfacing work to be done by later contracts. This permitted the newly graded embankments to settle for a couple of years before placing surfacing materials. It was advantageous to let nature compact these embankments over a period of time because many States still did not use effective compaction procedures in their grading work. This also permitted the natural stabilizing of any slips and slides that might occur in the generally steep back slopes which were employed at that time in roadway excavation.
Between 1926 and 1944, BPR and the American Association of State Highway Officials (AASHO) worked with various associations in the highway industry toward the common goal of building more and better highways. For example, the Portland Cement Association (PCA) contributed financially to the establishment in 1929 of the Cement Reference Laboratory by the National Bureau of Standards in cooperation with the American Society for Testing and Materials (ASTM). The PCA was also instrumental in the development of soil cement for low-cost surfacing.[16] AASHO published the first edition of their materials books in 1931, and then in 1940 and 1942 they published their Standard Specifications for Concrete Pavement and Bituminous Surface Treatment, respectively. In the 1920’s and early 1930’s, the Asphalt Institute, in cooperation with the BPR and various other public agencies, standardized asphalt cements and liquid asphalt products, thus, greatly reducing the number of grades and thereby facilitating the writing of asphalt specifications. Also, the Asphalt Institute in cooperation with the American Farm Bureau Federation was instrumental in initiating a program of paving farm-to-market roads. Like the capillaries of one’s blood system, these feeder roads played an important role in the transportation system of today.[17] In cooperation with public highway authorities, all of the industry associations, in one way or another, were major contributors to the tremendous development of highway construction during this period.
Constructing a stabilized soil road. A scarifier prepares road for the mixing of soil and cement.
Modernization of Roadbuilding
Probably the two most important advances in modernizing construction equipment during the 1920’s and 1930’s were: (1) The introduction of the diesel engine on tractors and graders in 1931, and (2) the development of large pneumatic tires which were used on scrapers as early as 1932, and on dump trucks in 1934, making it easier to operate on soft ground off the highway.
In the 1940’s self-powered equipment for onsite material stabilization was developed. This machine mixed soil and cement and added water to create a stabilized base.
Earthwork equipment became heavier and more powerful in the late 40’s and 50’s. Here a loader with a front-end scoop handles rock.
Bulldozer in action.
In other developments of construction equipment, the front apron was first placed on scrapers in 1933, making a 12-cubic yard load possible. Hydraulic controls were placed on power shovels in 1937, then in 1938 the self-propelled scrapers made it possible to move earth at a much faster pace. The compaction of earth was also keeping pace as the ballastable rollers were introduced in 1936. Paving equipment was being revolutionized as the traveling concrete paver, introduced in 1926, made use of the skip lever to activate the water measurement and the timing of the mix. In 1932, the dual-drum traveling paver helped to increase production of concrete for pavements. Internal vibrators for portland cement concrete were patented in the United States in 1935 and soon used widely to assist in the consolidation of concrete in the forms. Bituminous paving equipment was being developed as the road mix machine was introduced in 1929, and the bituminous paver placed on the market in 1932. This equipment provided more rapid construction of improved asphalt pavement at lower cost.[18]
Silver Lining of the Depression Cloud
As can be seen, many of these developments took place during the Depression years, when so many industries were virtually shut down because of the national economic situation. The highway industry was probably one of the industries that was least injured by the Depression. By using highway work as one of the “make work” projects of this period, the National Recovery Act brought employment close to the homes of the unemployed. It was estimated that for every person directly employed on road work, there were two others employed in the manufacture and transportation of road materials and equipment.[19]
Thus, while being used as one of the “tools” to fight the unemployment of the Depression, an added benefit was that the highway industry grew in capacity and was ready for the program of interregional highways that was recommended by the report Toll Roads and Free Roads in 1939. The program discussed in the report became the basis for the plan of the National System of Interstate and Defense Highways as we know it today.
A self-propelled, self-loading scraper.
World War II Disrupts the Highways
The Interstate program had to be postponed, however, as the country plunged into World War II. The Nation’s roads took a hard beating during the war years, as construction and maintenance were slowed considerably. The road work accomplished was largely composed of correction of critical deficiencies on main highways essential to war transportation.
All noncritical highway work was deferred, and the use of critical materials was reduced to a minimum. New construction was largely confined to access roads to new military installations, defense plants, ports and the like. World War II left its imprint on the highways. Many miles of the oldest highways, already worn and obsolete and scheduled for replacement, were kept in service. This situation, already bad, was accentuated by the wear and tear of continuous streams of war traffic. Thus, the mileage of roads no longer adequate for the traffic carried and difficult to maintain in service, grew in size throughout the war.
Due to the loss of personnel by State highway departments to the military forces and defense plants and the unavailability of new equipment, spare parts, tires and fuel, it was necessary for most States to sharply reduce their maintenance activities.[20] The quality of maintenance suffered. Only routine surface maintenance, resurfacing, and resealing were intensified to preserve the existing surface, whatever type it happened to be. Operations to maintain shoulders, clean ditches and culverts and mow the weeds were performed only as time, manpower, and equipment allowed.[21]
1944 to 1964—The Push For More Production
As the war in Europe neared an end, Congress passed the Federal Aid Highway Act of 1944. This was a far-reaching piece of legislation. It authorized $500 million for each of the first 3 postwar years; it authorized, for the first time, the use of Federal-aid highway funds in urban areas ; it provided authorization for the construction of a Secondary Road System; and it directed the designation of a National System of Interstate Highways. The funds authorized in this legislation made possible an expanded and essential program of construction and reconstruction of highways which had borne the burden of heavy wartime traffic with a minimum of maintenance or betterment activity.
This grader was designed to be as flexible as the human wrist. The blade shown here is especially useful for fine grading on slopes and ditches; a bucket blade is used for excavation work.
This period of 1944–64 was one of greatly expanded highway activity. Public Roads worked closely with the AASHO, the Highway Research Board (HRB), and the various industry associations, especially in the areas of coordination of construction practices, research, and the development of standard specifications.
In 1948, AASHO published its Policy on Maintenance of Roadway Surfaces (revised in 1961). Then in 1949, AASHO came out with its Manual of Highway Construction Practices and Methods. These two publications were a great help in distributing information to the States so that all could benefit from the successes that some States were having in their construction and maintenance procedures.
An elevating grader picks up material and conveys it to a waiting truck.
In 1960, AASHO published its guide on project procedures, and in 1963, it published the first Guide Specifications for Highway Construction, which became the national standard for highway construction specifications.
During this period, there were also tremendous advances in the productivity of highway construction. One of the big advances was the development, in 1945, of self-powered equipment for onsite material stabilization, which greatly increased the productivity and control of stabilized bases and subbase courses. The rubber-tired bulldozer, first placed on the market in 1947, and the vibrating roller, introduced in 1948, proved to be very successful. In rock excavation, the new carbide insert on rock bits was a tremendous help in lengthening the life of these bits. The application of hydrostatic drive to construction equipment was also being developed. In earthwork, as well as all phases of construction as a whole, the equipment manufacturers were continuously developing heavier and more powerful units to obtain more production at less unit cost for a better quality highway.[22]
Compaction is important in preparing a firm highway foundation. This compactor has pneumatic-tired, vibrating rollers which are particularly effective in compacting granular soils.
A paving train in Iowa in 1949 utilized dry batches dumped in to two twin-batch traveling mixers.
For this paving operation, concerte was hauled from a central mix plant and poured into the spreader from a side dump (bin).
The array of road construction equipment that was available at this time was huge and diverse, but every unit was developed in an orderly fashion to fill a definite need.
Significant advances in paving equipment were started. In 1955, electronic controls were put into use in concrete batch plants, simplifying and giving better control over batching. The triple-drum concrete paver, which could produce 125 batches per hour compared to 87 batches for the dual-drum, was introduced in 1959. Central-plant mixing with hauling by agitator trucks was used on large concrete paving projects. Transit mixers were widely used in urban paving and bridge work. Slipform pavers became widely accepted on highway work. Spreading and finishing equipment were developed to do a faster, better job. The use of central-plant mixing and slipform paving methods made possible some astonishing achievements in concrete pavement. Some road contractors reached the production rate of paving more than a mile per day of 24-foot wide, 9-inch thick Portland cement concrete pavement with this type modern equipment. This led to the “Mile-A-Day Club,” sponsored by the American Concrete Paving Association. In 1973, one contractor set a new record by paving 4.7 miles of 8-inch thick, 24-foot wide concrete pavement in a 23-hour period—14,853 cubic yards of concrete.
In the early sixties, automatic slope and grade controls for asphalt paver screeds were developed. Rolling equipment for bituminous pavements showed little apparent change over the years, but in reality improvements were developed for these machines during this period which made them faster, more productive, and easier to operate.
Other innovative developments included a helicopter designed to hoist and haul a 6-ton payload for construction work in inaccessible areas, and a vibratory sonic pile driver that could drive and pull piling at a small fraction of the time needed with conventional equipment.
In 1958, there were over 12,000 Federal-aid highway projects awarded at a total cost of about $3.5 billion to build or improve nearly 34,000 miles of roads. In 1964, approximately 7,000 Federal-aid projects were awarded at a total value of about $4 billion, corresponding to 18,300 miles of roads. The average size contract in 1958 was almost $300,000 and in 1964 was about $560,000—nearly doubled—while the total annual miles dropped. Obviously the trend was to shorter, more costly projects. In general, the longer rural, less costly Interstate projects were built first with the more costly and shorter urban projects following.
The high degree of mechanization of highway construction activity enabled construction labor to increase production greatly while reducing the number of man-hours required per mile of highway construction. The cost of highway construction over the years, in fact, has risen quite slowly as compared to the cost of labor and materials.
The paving train’s screw spreader.
1964 to 1974—An Increased Emphasis on Social Goals
By 1964 the Interstate program was in full swing. While highway mileage accomplishment for the Interstate was still the main goal, attention was focusing on other aspects such as highway safety, highway beautification, and consideration of wildlife and recreation areas, as well as historic sites. Environmentalists and ecologists were instrumental in keeping environmental concerns, potentially affected by construction, at a high level of consciousness among highway builders. New construction procedures were developed whereby detailed programs were implemented in order to reduce to a minimum the soil erosion during the construction process, and several States were investigating improved methods of sediment control for future highway construction use.
Studies were undertaken to investigate new equipment and other means to control noise and air pollution during the construction process. The dryer-drum process for hot-mix asphalt plants and better mufflers for heavy equipment were developed in an effort to reduce or eliminate these types of pollution.
There was an increased emphasis on highway safety. New safety devices were built into new highways, such as sign posts that broke upon impact, safer guardrails, and crash cushions which absorbed the shock of a collision with fixed structural elements.
Activities on construction projects were also changing. Construction contractors in some States were being required to furnish completely equipped laboratories and do their own surveying and layout staking, jobs which had previously been done by State highway departments. More States were using aerial photography and new data processing procedures to speed up monthly estimates.
The highway construction industry developed a greater awareness of public need and good public relations. Soil erosion prevention and other environmental and ecological aspects became integral parts of construction practices. Ways were studied to help the construction labor force also. Where possible, activities such as winter concreting techniques were developed to help extend the construction season and to give workers more yearly income, and occupational safety measures were adopted to improve the working conditions for the construction work force.
A slip form paver eliminates the need for setting steel forms, since the forms move along with the paving machine. A relatively stiff concrete is used so that, by the time the machine passes on, the concrete will hold its shape.
Bridge deck construction has become increasingly mechanized. This finishing machine permits the use of stiffer concrete and produces a smooth deck surface.
Grading equipment had greatly improved by the 60’s and 70’s. This motor grader is not only self-propelled, but also has enough power to push a scraper.
Conflict for Space Brings New Maintenance Era
As highway facilities became more and more congested and more people with their respective vehicles were fighting for this precious space on the streets and highways, the public began to resent the highway worker with his equipment taking up space on the public right-of-way, even if it did have to be maintained. The cry was: “Can’t you find some other time to do that; you can’t block the road at this time of day.” So a new emphasis was placed on road maintenance. Maintenance organizations were subjected to numerous external pressures which caused severe internal stresses. Because a maintenance management science had not been developed as fast as the technological improvements or sociological needs, the existing management was not able to cope with the problems of reporting systems, work methods and procedures, performance in terms of quality, quantity and productivity, and planning and scheduling work. An organized formal research program was expanded considerably during this period, with studies covering a wide variety of subjects.
In Virginia between 1963 and 1965, a Federal-aid study was designed to cover nearly every aspect of maintenance management. It involved the collection of data concerning performance of labor and equipment; development and testing of various work methods; establishment of quality, quantity and performance standards; development and testing of a new reporting system; development and testing of a budgeting system; and development and testing of training materials. Other simultaneous studies were in progress which zeroed in on various aspects of maintenance management.
Scraper being pushed by two tractors. Push-loading speeds up the process of loading and hauling heavy materials.
The basic components of maintenance management systems derived from these studies have been accepted by approximately 30 highway maintenance organizations. Such a system enables a highway department to prepare a performance budget showing specific maintenance activities and the resources in personnel, materials and equipment required to carry them out. On this basis, the highway department can develop long-range plans for maintenance operations and evaluate performance of the various field organizational units. This, in turn, indicates where additional training is needed. Furthermore, such a system provides the manager with the information needed to insure that equipment is being used efficiently and effectively, and to aid him in selecting the best unit for the work to be done.
Grading operations on Interstate 94 in North Dakota. After a water distribution truck moistens the soil, sheeps foot and ballastable rollers compact it.
Since 1971 the Federal Highway Administration, when requested, has assisted State organizations interested in discussing the basic components of a maintenance management program. State highway maintenance organizations that have implemented a maintenance management system are presently reviewing management practices in equipment management and capital outlay programs and are establishing district and area boundaries for related maintenance programs.
Advances in Equipment and Techniques
Construction industry associations were instrumental, as in previous periods, in the development of new equipment in such areas as tamping and vibrating rollers to speed up compaction of embankments and base courses. The use of nuclear devices for testing compaction on soil and base courses became more widespread as these devices made this type of testing much faster. Large screw augers were being used more frequently for structure foundation excavation. New equipment developed for subsurface investigation made it possible for more precise bidding on excavation work, because the contractor could depend on more accurate subsurface information.
The laser beam has become a very useful tool for engineers in establishing line and grade for pipe laying, eliminating the need for off-set lines and batter boards. New methods of making pipe and specialized equipment for cleaning pipe have also come into use during this period.
New methods for handling concrete, such as concrete pumps and new deck finishing equipment, have made bridge work more productive and enabled contractors to produce safer, smoother riding bridge roadways. Stay-in-place steel forms for concrete bridge decks were developed and thereby eliminated the need for the removal of the forms, an often hazardous and difficult operation.
Precast concrete units such as culverts and barricades came to be widely used, also.
Spreading and finishing equipment for pavements were developed into quite sophisticated machines that eliminated much of the hand work. New types of equipment for texturing and grooving concrete pavement surfaces came into use to help provide more skid resistance.
Large automatically controlled, central-mix plants were quite extensively used in concrete pavement work in this period from 1964 to 1974. Some States permitted asphalt plants to operate without screens, using variable speed belts and multiple cold feed bins for gradation control. Also, some asphalt plants were equipped with surge storage, which allowed them to produce asphaltic concrete continuously without having to stop the plant to wait for haul trucks. The development of practical electronic systems for automatic grade controls, which used sensing devices to follow a string-line or guide-wire, was very important.
Significant advances in equipment in nearly every field of use were seen during this period in an effort by the industry, as a whole, to obtain faster, more efficient production with less “down time.”
Many advances have been made in developing new materials and techniques for highway construction. A new technique of presplitting faces of road back slopes before blasting for excavation gave a much more even back slope in rock cuts. Various treatments, such as lime and water-proof membranes, were put into use to help overcome the problems of swelling soils. Even though they had been in use for many years, synthetic aggregates were seeing more use in highway work during this period. New types of coatings for structural steel and culvert pipe, as well as pipe jointing materials, were being produced. Additives for concrete that controlled the set for better workability and that produced more durable structures were being further developed. Even so, concrete bridge decks were beginning to show signs of early deterioration, caused by salt used as a de-icing agent penetrating the concrete and destroying the reinforcing steel. This brought about specialized construction methods for the protection of bridge decks, such as the use of epoxy coated or galvanized reinforcing steel and waterproof mastics or membranes.
During the years from 1967–1974, highway builders were finding an increasing scarcity of key highway construction materials, such as cement, steel, asphalt, and paint, which accelerated the search for alternate materials. Gasoline and diesel oil for the big rigs also became scarce, especially during the oil embargo late in 1973 and early 1974. The use of some waste materials in highway construction helped stretch existing supplies somewhat. For example, some States started using fly ash as a substitute for some of the cement in concrete mixes. Some experimented with rubber from old automobile tires to modify asphalt in hot mixes.
Now the United States has become a Nation bound together by an extensive ribbon of efficient well-maintained, quality streets and highways. Where once the horse and wagon slowly plowed through muddy roadways, millions of cars and trucks swiftly carry people, goods, and services to every corner of this country, impacting the social and economic wellbeing of every community. The ability to steadily obtain more production and an improved quality of construction and maintenance of this Nation’s streets and highways while still preserving a reasonably level cost is due to the combination of the many factors of the construction and maintenance system as it has developed. Some of these factors, which have been discussed, are the competitive bidding mechanism, the improved managerial methods, a dependable public financing, the advancing technology, and the motive force of the State and Federal Governments in desiring to meet the needs of the Nation and her people.
However, though the capability and motivation were present, the success of this effort required the excellent cooperative spirit that existed among the Federal Highway Administration and its predecessors, the State highway departments, and the industry associations. Without this partnership, there would not be the sound construction industry or the effective highway network that we have today.
Hanging a girder during construction of a three-level interchange in Dallas, Tex.
A twin box culvert under construction.
REFERENCES
- ↑ A. C. Rose, Historic American Highways—Public Roads of the Past (American Association of State Highway Officials, Washington, D.C., 1953) p. 100.
- ↑ Id., p. 101.
- ↑ Id., pp. 103–105.
- ↑ G. Galli, 100 Years of Construction News—Events That Shaped the Future, Engineering News-Record, Vol. 192, No. 18, Apr. 30, 1974, p. 455.
- ↑ A. C. Rose, supra, note 1, p. 108.
- ↑ Public Roads Administration, The Public Roads Administration and Its Works (Federal Works Agency, Washington, D.C., Revised Nov. 1946) p. 3.
- ↑ Bureau of Public Roads Annual Report, 1918, p. 5.
- ↑ P. Hubbard, Efficiency of Bituminous Surfaces and Pavements Under Motor Truck Traffic, Public Roads, Vol. 1, No. 10, Feb. 1919, p. 25.
- ↑ A. P. Anderson, Modern Road Building and Maintenance (Hercules Powder Co., 1921), pp. 33, 103.
- ↑ PRA, supra, note 6, pp. 25–27.
- ↑ Bureau of Public Roads Annual Report, 1926, p. 32.
- ↑ Id., pp. 34–35.
- ↑ Civil Engineering Department and the Transportation Engineering Center of the Ohio State University, Proceedings of the Sixteenth Annual Ohio Highway Engineering Conference (Columbus, Ohio, Apr. 2–4, 1962), pp. 13–14.
- ↑ G. Galli, supra, note 4, p. 455.
- ↑ Ohio State University, supra, note 13, p. 27.
- ↑ 50th Anniversary of PCA, Civil Engineering, Vol. 36, No. 3, Mar. 1966, pp. 32–42.
- ↑ The Asphalt Institute—What It Is and What It Does, Information Series 110, (The Asphalt Institute, College Park, Md., Jun. 1973).
- ↑ G. Galli, supra, note 4, pp. 455, 456.
- ↑ Bureau of Public Roads Annual Report, 1931, pp. 1–7.
- ↑ Southeastern Association of State Highway Officials, Proceedings (Chattanooga, Tenn., 1943) p. 75.
- ↑ Convention Group Meetings—Papers and Discussions (St. Louis, Missouri, Dec. 1942), (American Association of State Highway Officials, Washington, D.C.) p. 76.
- ↑ G. Galli, supra, note 4, pp. 455–459.