Estimation of 18-kip Equivalent on Primary and Interstate Road Systems in Virginia

About the report:

For pavement design purposes, the Virginia Department of Highways uses the AASHO method of determining the 18-kip equivalent single axle load (EWL-18). The evaluation of the EWL-18 is based on on-location truck axle weight studies that usually are carried on for one day only. This method is expensive and time consuming. Because of the expense and time involved in the initial evaluation of the EWL-18, no attempt is made to reevaluate it during the life of the pavement, even when rehabilitation is proposed. For this reason, a method by which the EWL-18 could be quickly estimated from the routinely available records seemed desirable. The Virginia Department of Highways issues yearly reports on (i) the traffic count on each section of the primary, interstate and arterial system, and (ii) the weights of vehicles using these systems. In this investigation, several methods were tried to determine the best method for estimating the EWL-18. A method involving 3 equations was found to have the best correlation with the AASHO method. This method is very flexible and accounts for the weight and count of each vehicle type. It is also shown in this report that even if the estimated EWL-18 deviates greatly from the AASHO value, the effect on the ultimate pavement design is very little. It is therefore recommended that this method of estimating the EWL-18 be used in connection with pavement rehabilitation studies when EWL-18 values are not currently available. The approach may be applied to develop traffic projections in cases where loadmeter studies are not feasible.

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