The attached report presents significant progress and achievements in the area of asphalt pavement design. Benkelman beam deflections were used extensively in conjunction with our 1958 study of asphalt pavement performance; apparent relationships between 18–kip deflections and pavement structures were evident then although scatter in the data was thought to be necessarily admissible. During the spring and summer of 1966, another extensive series of pavements, built since 1958, were evaluated from the standpoint of performance and deflection. It seemed compelling at that time to adjust all deflections to some common reference temperature and so the surface temperature of the pavement was measured at each test site at the time the deflection test was made. However, the development of a temperature-deflection adjustment factor became more complicated than it was expected to be. It became rather evident that surface temperature alone would not suffice. Since temperatures were not measured at depths and since subsurface temperatures were thought to influence deflections greatly, a method of approximating or estimating temperatures at depths was desired. This became the first objective; the second objective then was to determine the magnitude of the adjusting factor.

Report Date


Report Number

No. 253

Digital Object Identifier



The opinions, findings, and conclusions in this report are not necessarily those of the Department of Highways or the Bureau of Public Roads.