70 km/h Speed Limits on Former 90 km/h Roads: Effects of Sign Repetition and Distraction on Speed

Abstract

Objective: It was investigated how speed limit repetition and distraction affect drivers' speed management throughout a road section where the imposed speed limit is not in accordance (too low) with road design. Background: It is not clear how driving speed evolves and to what degree speed limit repetition is necessary on roads where the imposed speed limit is not in accordance (too low) with road design. It is furthermore of interest how all these factors are influenced by driver distraction. Method: In a driving simulator, 47 volunteers completed one trip with and without distraction. Within each trip, three configurations were presented: speed limit sign repetition after every intersection, repetition only in the middle of a segment, or no repetition. Results: Distraction lowered driving speed. Speed management varied depending on speed limit repetition. The speed limit was exceeded more often when speed limit signs were repeated less frequently. When drivers were not reminded of the limit, speed linearly increased throughout the segment. In all three configurations, speed increased toward the end of the segment, but this increase was largest when there had been no repetition at all of the speed limit. Conclusion: In low-demanding road designs that allow drivers to exceed the speed limit, limit repetition is necessary. Frequent repetition may be preferred, as speed management was most homogenous in that case. Application: The proposed analysis of speed management throughout a section increases our understanding of how speed evolves and thereby shows where repetition of the speed limit is necessary.