Estimation of Equivalent Axleloads

The primary objective of this research study was to develop a procedure for estimating equivalent axle loads for purposes of flexible-pavement design. Maximum use was made of historical data and well-accepted procedures were used in developing the prediction model. A series of computer programs was developed to summarize truck-weight and classification data such that traffic characteristics could be estimated from a matrix of data classified by geographic area, Federal highway system, volume, and extent of coal haulage. An equation was developed with the following seven parameters as independent variables; 1) annual average daily traffic volume, 2) average fraction of trucks in the traffic stream, 3) average fraction of coal trucks in the total truck population, 4) average number of axles per coal truck, 5 ) average number of axles per non-coal truck, 6 ) average number of equivalent axleloads per coal-truck axle, and 7) average number of equivalent axleloads per non-coal-truck axle. The equivalent axleload estimate was calculated from estimates of the seven traffic parameters. The procedure for estimating equivalent axleloads was found to be a simple one that yields reproducible results while allowing great flexibility in merging site-specific data with statewide averages for roads of similar type. Location-to-location variability was recognized and a recommendation was made to incorporate site-specific data into the design estimate whenever possible