by urban and industrial interests, also recommended that gross loads of 14 tons be permitted on the highways provided the load per inch width of tire did not exceed 800 pounds.[N 1]
Launching a National Highway Research Program
The matter was brought to a head in August 1919 by Thomas R. Agg, Testing Engineer of the Iowa State Highway Commission, who wrote in an article for Public Roads magazine:[N 2]
During the past 10 years, the transition from horse-drawn to motor traffic has been so nearly complete that horse drawn-traffic can no longer be considered a controlling factor in highway design ; yet practically all of the basic principles of highway construction were evolved for horse-drawn traffic. These have been modified from time to time as experience has indicated defects, but for the most part local conditions have been so large a factor that types and designs which have been satisfactory in one State have proven entirely unsatisfactory in another. . . .
It seems imperative that investigation in the field of highway engineering be prosecuted with the utmost vigor during the next few years, else it will be found that much of the money expended for highway improvement has not secured highways of the maximum serviceability because the design and the requirements for materials were based on unsound theories or inadequate tests.[2]
Agg then urged that the Bureau of Public Roads take the lead in a national program of highway research:
The bureau has already done a large amount of research work in this field and has trained investigators for carrying on the work and for passing on projects submitted for action . . . But most important of all, the bureau is in close touch with the highway work in the various States and is in a position to judge as to the problems most imperative of solution and to secure the assistance of the State highway departments in those problems requiring the actual construction of surfaces or structures.[3]
In a companion article, A. R. Hirst, President of AASHO, not only endorsed Agg’s proposal but pledged AASHO’s support “for this very great and necessary work.”
I agree thoroughly with Mr. Agg in his statements that the present facilities for highway engineering investigations are not adequate to meet the situation, or to develop the theories upon which the future science of highway engineering should be based. It is to my mind certain that unless the United States Bureau of Public Roads builds up a good and extensive organization to prosecute these inquiries, that nothing of value can or will be done by any other existing organization.[4]
- ↑ The 800-pound figure was recommended by tire manufacturers as the maximum economic loading for solid truck tires. Heavier loads would, they said, cause crushing of the rubber and premature failure by fatigue. At this time the widest tire manufactured was 14 inches, so the maximum load that could economically be carried by a two-wheel axle was 22,400 pounds.[1]
- ↑ Public Roads was an official publication of the U.S. Department of Agriculture. It had been launched in May 1918, by Logan Waller Page as a vehicle for exchange among the States of information on methods for financing, building, and maintaining roads. By 1919, Public Roads was an important voice for the highway engineering profession and also, in effect, the journal of AASHO, which did not have its own publication, American Highways, until 1922.
Truck damage to roadways led to a coordinated national research program by 1920.
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