Paper presented at the 32nd Annual Southern African Transport Conference 8-11 July 2013 "Transport and Sustainable Infrastructure", CSIR International Convention Centre, Pretoria, South Africa.
Very little research has been done in South Africa on the speeds of trucks on downgrades.
However, a thorough knowledge of this subject is essential in a number of areas namely the justification of arrestor beds and escape lanes for run-away trucks, the development of speed profiles on roads and the provision of passing lanes on downgrades.
In a recent study in the Western Cape the speeds of trucks were measured on various downgrades related to mountain passes. Two types of downgrades were investigated namely those that are followed by a straight section of road on an upgrade and those that
are followed by a section with restricted horizontal alignment and sight distance. Since it
was not possible to determine the mass of the trucks the number of axles was used as a
substitute for the size of the trucks.
The paper will describe the data collection, analyses and the results of the analyses for the
two different cases and the different axle classes.
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