Effects of speed limit variation on judged mean speed of a trip

Three experiments were set up to study how drivers estimate mean travel speeds on trips with different speed limits. To specify, participants judged mean speeds of trips with speed limits on different distances of the trip. Study I showed that the mean speed on a road with a temporary 30km/h speed limit was overestimated if the speeds were greater than 80km/h on the rest of the trip. Study 2 replicated and extended the results to problems with more speed combinations. In Study 3 the distances of the speed limits were varied and the results showed that a temporary 30km/h speed restriction gave overestimations of the mean speeds of a trip for all combinations of original and temporary speed limits over all distances. Finally, some psychological issues and applied implications for speed regulation policies were discussed. (C) 2009 Elsevier Ltd. All rights reserved.