Accelerated Pavement Testing (APT) can be described as a controlled application of wheel loading to a pavement structure for the purposes of simulating long-term, in-service loading conditions. Factors critical to this simulation of in-service pavement conditions are that the loading configuration and method of loading be realistic with that encountered by in-service pavements.

APT allows for the monitoring of pavement performance and response to accelerated accumulation of damage within a shorter time frame, providing pavement engineers with valuable information concerning the behaviour, performance, and life expectancy of pavement structures. This ultimately results in enhanced understanding of pavement structures and improved, cost effective design and rehabilitation construction methods.



APT furthermore provides a controlled testing environment in which innovative pavement designs and new materials can be tested and validated in a short period without the financial risks associated with failures of in-service experimental pavements.

APT can be traced back to the AASHO road test, still regarded as one of the most comprehensive investigations of the performance of pavement systems. The costs involved with such full-scale APT testing on test roads using actual traffic initiated research into alternative methods of APT. Currently APT is differentiated into three main categories namely: full scale test roads; mobile APT units; and fixed APT units. Full scale test roads are APT facilities at which actual vehicle traffic is utilised for the application of loading.

Mobile APT units are load frames with variable axle and wheel configurations designed to simulate the load application of actual vehicle traffic on a limited test section. Mobile APT units can be transported to various locations for testing and are applicable to the investigation of in-service pavements in addition to specifically constructed test sections.

Fixed APT units also utilise load frames for load application but have a fixed location and cannot be transported easily to various testing locations.

What is the Heavy Vehicle Simulator?

The Heavy Vehicle Simulator (HVS) is a fully mobile APT unit capable of simulating 20 years of traffic within a period of 3 months.



Developed by the South African Council for Scientific and Industrial Research (CSIR) with assistance from the South African Department of Transport and the then Transvaal Provincial Administration (now the Gauteng Department of Public Transport, Roads and Works), the HVS provides a mobile laboratory with the ability to accurately and cost effectively test and monitor pavements under a variety of environmental and loading scenarios.

What differentiates the HVS from other similar APT units is the continued research and improvements made to the unit over the last 3 decades. From its meagre beginnings as a fixed linear tracking pavement loading device the HVS evolved into a fully mobile APT unit that has gained worldwide recognition and lead to numerous innovations in development of monitoring devices for APT testing. These monitoring devices have in turn improved the capability of the HVS system to accurately simulate and record pavement performance.



The HVS weighs approximately 46 tons with dimensions of 22.6 m x 3.5 m. It is capable of applying wheel loads varying from 4 tons to 30 tons per axle (nearly four times the national legal maximum), through a standard half axle dual truck tyre configuration or modified aircraft wheel configuration.

Four operational models have been manufactured: the Mk III, Mk IV, Mk IV+ and HVS-A. The Mk IV+ unit is closely aligned with the Mk III, but provides full computerized control and limited simulation of dynamic loading in addition to increase productivity (32 000 repetitions/day compared to 16 000 repetitions/day of the Mk III). The HVS-A is a super heavy duty version of the HVS developed specifically for the simulation of the high loads applied to airport and harbour pavements and other similar facilities.

Gautrans was the first provincial roads authority worldwide to operate a fully mobile APT unit in the form of a HVS Mk III in 1978. This association between Gautrans and the HVS continues until this day with the recent acquisition by Gautrans of a HVS Mk IV+. Internationally, 2 Mk III, 3 Mk IV and one HVS-A are currently in operation.

Currently comparative testing is in progress with the old MK III HVS and the new Mk IV+ unit at the HVS test site on Road D2388 near Cullinan.