An experiment in the driving simulator compared two ways of presenting congestion information on motorways by means of dynamic signing. The first way of doing so was by means of three-line text-panels (`DRIPs'), which are already in standard use on Dutch motorways. The second way was by means of graphic signs, showing the geometry of the road network on which the current congestion pattern is displayed (`GRIPs'). 48 subjects drove in the simulator in a number of scenarios in which they encountered both DRIPs and GRIPs. Half of the subjects were good map-readers, according to their own judgement, and the other half were low on this skill. There were three road networks differing in complexity (Utrecht, Arnhem and Amsterdam). Also, the congestion information presented on the panels had different degrees of complexity. The performance of subjects was measured on three dimension. Conclusions are drawn. On basis of these conclusions it is recommended that a field test of GRIPs be performed as a step leading to their possible implementation. This should be a long-term evaluation. There is no reason to fear for an increased safety risk, as the results of this simulator study have shown. (A)
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