Performance-based standards for South African car-carriers
Date
2013-01-31
Authors
de Saxe, Christopher Charles
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Abstract
Until recently, car-carriers in South Africa operated under abnormal load permits
allowing a finite relaxation of legal height and length limits. This practice is being phased
out, and exemption will only be granted if a car-carrier complies with the Australian
Performance-Based Standards (PBS) scheme. A low-speed turning model was developed
in Matlab®, and used to benchmark the tail swing performance of the existing South
African car-carrier fleet. About 80 per cent of the fleet were shown to not comply with
the 0.30 m tail swing limit, due to South Africa’s inadequate rear overhang legislation
which permits tail swing of up to 1.25 m. TruckSim® was used to conduct detailed PBS
assessments of two car-carrier designs. Critical performance areas were identified; most
notably yaw damping and tail swing for the truck and tag-trailer combination, and
maximum of difference and difference of maxima for the tractor and semitrailer
combination. These were remedied through appropriate design modifications. The
Matlab® model was shown to be versatile, accurate and efficient, with potential for future
application. The TruckSim® assessments highlighted complexities unique to car-carriers
in a PBS context and showed how these may be addressed. This research has shown the
benefit of PBS for heavy vehicles, and has guided car-carrier design to improve safety.