Maximum of difference assessment of typical semitrailers: a global study

Abstract

Tractor semitrailer car-carrier designs operating in South Africa are required to demonstrate Level 1 compliance as legislated by the Australian PBS in order to be granted productivity concessions. A stumbling block in demonstrating compliance has been the Maximum of Difference (MoD) performance measure, which must be no greater than 0.40 m. The MoD performance of 480 tractor semitrailer combinations were analysed. The study compared the MoD performance of semitrailers specified to have the maximum allowable width and frontal overhang as stipulated by legislation from Australia, the European Union, Canada, the United States and South Africa. The majority of the Australian, EU and Canadian semitrailer combinations and all of the South African semitrailer combinations analysed did not demonstrate performance within the MoD limit of 0.4 m set by the Australian performance based standards. This would suggest that the MoD limit of 0.4 m is overly strict. An MoD limit of 0.6 m is suggested as an appropriate limit to be implemented in South Africa