Too fast for these conditions? Factors influencing drivers’ choice of speed

The choice of inappropriate speeds by drivers is one of the oldest and most difficult road safety issues. This paper describes the results of two experiments investigating the factors influencing drivers’ choice of speeds on rural roads. In the first experiment the influence of trip purpose and individual differences on speed choice was examined. The results showed large differences between speeds chosen for different driving purposes; the lowest speeds were chosen when the goal was economy and the highest when driving for fun. In addition, there were individual differences in speed preferences such that some drivers indicated that their usual speed was above what they believed was a safe speed while others indicated that they usually drove even slower than what they thought was safe. The second experiment investigated the relationship between the visual appearance of rural roads and drivers’ choice of speed on those roads. Previous research has shown that how a road looks can affect drivers’ perception of their speed, and as a result influence the speed they choose, in some cases without them being aware of it. In this experiment drivers completed a picture sort task and then indicated their preferred speed, safe speed, and likely speed limit for 34 rural road scenes. The results indicated that perceived difficulty was the best predictor of participants’ speed choices. The results are discussed in terms of identification of road characteristics that can help distinguish behaviourally relevant road categories and produce better speed compliance independently of enforcement.