Load Characterization and Prediction of Entry into Perpetual Construction Domain for Highway Pavement Structures by Truck Factor Study

Abstract

This paper presents the results of pavement characterization study of a highway by Truck Factor and Axle Load Factor. The study highway is one of Nigeria’s most important corridors linking the South and the North of the country. The Truck Factor obtained is 9.30 Equivalent Standard Axle Loads (ESALs) while the average Load Factor per axle is 3.25 ESALs. These values particularly the Truck Factor are on the very high side in comparison to published figures in other countries. In the United States of America, published figures for Truck Factors for the rural Interstate highway system and rural principal arterials are 0.52and 0.38 respectively. That for the United Kingdom for similar roads is 2.75. Truck axle overload could therefore be one of the sources of prevalent premature pavement failures on this and similar highways in the country. Also, while single axles in the trucks carried a load of 2.29 ESALs each, tandem and tridem axles impacted the pavement with loads of 3.59 and 6.4 ESALs per axle respectively. If the study pavement were to be reconstructed for a design life of 20years, 66.05 million ESALs from truck axles would cumulate in this period as obtained from this study. This figure is more than double the 30million ESALs stipulated as the trigger load for perpetual or long life pavement construction. Therefore, the study highway should be reconstructed as such.