The effect of road crossfall on road wear caused by heavy vehicles

Abstract

The paved road network is a critical asset to any economy. South Africa has a paved road network that has an estimated value in excess of R2 trillion. This asset is however under threat as there was a backlog in maintenance of more than R197 billion in 2014. Heavy vehicles are primarily responsible for road wear, and overloaded vehicles can cause more than 60% of road wear. Most road wear assessments use static axle loads that are assumed to be symmetrical on either side in order to calculate the road wear caused by a heavy vehicle. This paper investigates the effect of road crossfall on the road wear caused by heavy vehicles, and compares it to the wear calculated using the static loading scenario. This was done by simulating four Performance Based Standards (PBS) vehicles and four conventional baseline vehicles. A representative road profile was used and the crossfall was varied from 0% to 5%. The average road wear from eight South African pavements was used to assess overall road wear impact. TruckSim® software was used to perform the heavy vehicle simulations, and the mePADS mechanistic empirical simulation software was used to perform the road wear simulations using the RMS axle loads from TruckSim®. It was found that crossfall values as low as 3% can produce a difference in road wear of more than 26.1% between the left and right sides. When comparing the road wear from a static analysis to the dynamic analyses, it was found that there is a substantial difference in the calculated road wear, even at low values of 2 to 3% crossfall, with a maximum difference of 59.3% recorded at 3% crossfall. It is therefore recommended that future road wear assessments incorporate the effect of vehicle roll motion and crossfall into road wear assessments.