Agg’s and Hirst’s appeal set the stage for a series of events that resulted in the formation on November 11, 1920, of the National Advisory Board on Highway Research, under the auspices of the National Research Council of the National Academy of Sciences. This Advisory Board was conceived as a means of bringing together in a coordinated national research program all the various agencies and organizations involved in highway transportation and highway research. The organization of the Board was completed July 1921 with the appointment of Dr. W. K. Hatt of Purdue University as Executive Director.
As his first job, Director Hatt prepared a list of 19 “fundamental questions in highway transport,” which, he said, could not be answered without data that then were unavailable. A few of these questions, listed below, illustrate the extent of the current ignorance of fundamental highway problems:[1]
- What is the economical highway track unit for each of the several situations, e.g., intercity, farm to market?
- What is the cost of transport arising from the vehicle and from the road?
- What type of road paving should be selected for a specific transport unit?
- How should the design of the road and paving be modified to meet changing conditions of subgrade, climate, etc.? How shall subsoils be improved?
- What sum of money is the locating engineer justified in spending to avoid increase in distance, curvature, rise and fall, maximum grade, maximum curve?
- What is the capacity of a road of given width as expressed in vehicles per hour, ton-miles per year, etc.? What is the appropriate unit for expressing traffic for various purposes?
- How can the volumetric changes in roads be overcome?
- What is the economic life of various types of roads?
- What police regulations should control the use of roads?
- What principles should govern the selection of a system of roads in its various parts, as influenced by interstate, intrastate, county or local traffic?
- To what extent do social betterment, military use, i.e., social value, and other imponderables enter into highway policy?
- How shall safety be ensured on the roads?
Hatt posed these questions at a meeting of educators and industrial leaders held at the University of Maryland in August 1921 and urged “a mobilization of the efforts, of research agencies in a comprehensive program,” adding that the National Research Council would be glad to coordinate the research but would not engage in research directly.[2]
At this time the Bureau of Public Roads was the only research organization that was prepared to immediately begin work on a large-scale research program, and, in fact, it was already working on some aspects of the program. The BPR had 13 major studies underway in the field of physical research and its research budget was about one-third of the total national expenditure on highway research.[N 1] Chief MacDonald took the lead in the national program by expanding the BPR’s in-house activities and also by entering into cooperative research agreements with State highway departments and universities.
The Fruits of Research
Throughout the 1920’s, with two notable exceptions, the brunt of the research effort fell upon the Bureau, primarily because it had the only large assured income available for the costly studies that were required.[N 2]
For about 5 years, the investigators concentrated mainly on soil and pavement research to provide immediately usable information to guide the vast paving programs that were already underway. As a result of these studies, all States stopped using thin, that is, 4- and 5-inch pavements and they rapidly adopted a 20-foot minimum width for main road pavements.[N 3] One of the major fruits of the research program was a rational method of analysis proposed in 1925 by Professor H. M. Westergaard of the University of Illinois, which removed much of the guesswork from slab design.
Out of the BPR soils investigations there came a practical system for classifying soils into eight groups based on physical properties that could be measured by simple laboratory tests. This was a tremendous step forward, for it enabled the researchers to relate pavement performance to measurable soil properties and, ultimately, to predict in advance of construction the type and depth of pavement that might be required for any field condition.
- ↑ In 1920, 22 State highway departments spent about $175,000 on research and 21 colleges and universities about $150,000. In addition, the BPR spent about $150,000.[3]
- ↑ The two exceptions were the Bates Experimental Road, financed by the Illinois Division of Highways, and the Pittsburg, California, Test Track built by the Columbia Steel Company with private funds. The Federal Highway Act of 1921 authorized the Secretary of Agriculture to deduct up to 2% percent of all Federal-aid appropriations for administering Federal aid “and for carrying on necessary highway research and investigational studies independently or in cooperation with the State highway departments and other research agencies . . .” From 1922 to 1932 the sums so set aside amounted to $1.87 million per year, of which probably one-half went into research. By contrast, the States were unable to use Federal-aid funds for research, because the Government’s policy was to approve the use of these funds only for construction.
- ↑ The Bates and Pittsburg Tests showed that narrower pavements channeled traffic near the edges and caused excessive corner and edge breakage. In 1928 the AASHO recommended in its first published road standards that the minimum width of one traffic lane be 10 feet. Other considerations, such as safety and freedom of maneuver at higher speeds, also entered into this recommendation. AASHO also recommended a minimum thickness of 6 inches for concrete pavements and the strengthening of all unsupported pavement edges in its 1928 standards.[4]
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