Traditional methods of speed reduction such as traffic calming and enforcement tend to have only local effects. A global speed reducing measure, Intelligent Speed Adaptation (ISA) which restricts drivers to the posted speed limit is being considered as an alternative. This paper reports a driving simulator study that evaluated the effects of such a system on driver behaviour. Measures of safety were taken when drivers drove with and without an ISA system, in addition to subjective measures of workload and acceptability. A number of changes in behaviour were noted, whereby drivers were more inclined to engage in riskier behaviour when the ISA system was operational. These changes were accompanied by reductions in maximum speeds, particularly in low speed limit areas and at speed limit transition points. It is suggested that the combinatory effects of these changes in behaviour have to be considered within the context of total network safety. (Author/publisher).
Abstract