Analysis of Axle Loadings on a Rural Road in Nigeria

Abstract

This paper presents the outcome of the axle load survey on a section of a rural trunk road in Nigeria in order to quantify the contribution of overloaded goods vehicle to pavement failures and propose appropriate amelioration strategies for vehicle axle system modifications. Seven day classified traffic and axle load survey was conducted for the determination of ADT, percentage heavy vehicles and the imposed axle load at respective axle position for each of the traversing vehicle on the old Jos – Kaduna road, Kaduna State Nigeria. The proportion of the vehicle laden weight carried by each axle and the corresponding standard axle load (sal) was computed with the index model of power 4. The percentage and magnitude of overloaded axles were respectively determined as a measure of an addition to the influence of the dynamic effect of moving wheel loads on a flexible pavement in the structural damage analysis of a pavement. The studied pavement was overstressed up to five times beyond the Nigerian standard axle load of 80kN, which was too high and hence probably constitute the hindsight to frequent structural damage to road pavement failure in a typical developing country, Nigeria. It was recommended that routine axle load survey and control with weigh- in-motion weighing bridges to assure protection of the road against failure or a complete redesign of the chassis of heavy goods vehicles meant for developing countries be effected. The two options may be considered for a more effective and proactive means of assuring the life of pavements and asset value. Also a review of the legal axle from 8.0 to 13.6 tonnes for the developing countries should be considered.