Paper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:A recent report from the Road Traffic Management Corporation (Botha, 2006) shows that the percentage of vehicles exceeding the speed limit on South African roads during weekends in December has increased from 24,1% in 2004 to 30,7% in 2005. This is a very high increase for a period of one year only. It is an internationally accepted fact that speeds do play a role in road traffic accidents and especially the severity thereof. It is therefore important to know what is happening to the average speeds of vehicles on our major roads.
In a recent study on the roads that are monitored by The South African National Roads Authority Ltd (SANRAL), longer term trends were determined – for some roads over ten years and for others over five years – depending on the period for which records are available. When it is considered that for some of the permanent stations the average value is calculated for at least a couple of million vehicles, it is clear that even the smallest change in the speed is statistically significant.
On the majority of urban freeways the average speeds of vehicles have decreased as a result of increased congestion. Mixed results were found on rural roads. On some the speeds decreased and on others it increased.
In the paper the background to the study and the results are given. Possible reasons for the different results are discussed and the consequences for road safety and delays are spelled out.
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