Photo of AASHO test section from Highway Research Board Special Report 61A-G The analysis of the work resulted in a guide that has been used ever since, the AASHTO Guide for Design of Pavement Structures (the “T” for “Transportation” was added in 1973).įigure 1. The same level of traffic caused differing amounts of distress to the different sections. Six pavement loops like the one shown in Figure 1, consisting of several different pavement cross sections, were continuously loaded to try to simulate a lifetime of fatigue in just a couple of years. In the late 1950’s and early 1960’s, a large-scale experiment was performed by the American Association of Highway Officials (AASHO).
Or they are simply empirically based – what has been observed to perform under similar conditions before.
Pavement thickness designs are too often based on economics – how thick can the pavement be built with the dollars available for the project, regardless of the engineering realities. “How thick should I specify the asphalt on my project, considering the number and types of traffic loads I expect, and the support I think the subgrade will provide?” That is the basic question posed by engineers who want their pavement to last a long time, and in good condition. By Guest Columnist Danny Gierhart of the Asphalt Institute
