The contribution of credible speed limits and ISA to speed control; A driving simulator study. This study examines the effect of credible speed limits on speed behaviour, with or without an Intelligent Speed Assistant (ISA). In-vehicle ISA provides information about the speed limit and warns when the driver exceeds it. The study was carried out in a driving simulator. A total of 41 subjects drove along a set of rural roads with speed limits of 60, 80, and 100 km/h. The credibility of the speed limits was manipulated by varying a number of road characteristics, being road width, presence of vegetation, and the type of separation of driving directions. These characteristics were identified in the literature as being relevant for speed choice, i.e. the intuitive speed. The credibility deviated from optimal in two directions: less credible because the speed limit is experienced as being too high for the road and its environ-ment, or because it was experienced as being too low. In the experiment, half of the subjects were supported by an ISA, and the other half were not.
Abstract