Improving the Safety and Road Wear Performance of Heavy Vehicles in South Africa Using a Performance-Based Standards Approach

Abstract

As a result of successful initiatives in Australia, New Zealand and Canada, the introduction of a Smart Truck or performance-based standards (PBS) approach in the heavy vehicle sector in South Africa was identified by the CSIR as a research area warranting funding because of the potential benefits in terms of transport efficiency, road/vehicle safety and the protection of road infrastructure. The PBS approach involves setting standards to specify the performance required from the operation of a vehicle on a network rather than prescribing how the specified level of performance is to be achieved. A need was identified to design, manufacture and operate a number of PBS demonstration projects in South Africa in order to gain practical experience in the PBS approach and to quantify and evaluate potential benefits. The Smart Truck demonstration projects have been designed and manufactured to comply with the safety standards of the Australian PBS system. These include directional and non-directional manoeuvres such as acceleration capability, slow speed swept path, static rollover threshold and rearward amplification. In order to evaluate the impact of the PBS vehicles on pavements, the South African Mechanistic-Empirical Design and Analysis Methodology was used to calculate the road wear characteristics of various baseline and PBS vehicle combinations. In most cases, the PBS vehicles were found to be significantly more road-friendly per ton of payload than the corresponding baseline vehicles. Modifications for reducing road wear were identified such as load redistribution in order to reduce the load on the steering axle, replacing wide-based single tyres with dual tyres and, where appropriate, replacing a single steer axle with a twin steer axle unit. The paper describes the results of road wear analyses of five PBS vehicles and the corresponding baseline vehicles.