Road safety can benefit from roads that are designed in a way that is self-explanatory for drivers. Indicating an appropriate driving speed is a main issue in self-explaining road design. Previous research has focused on the impact of different design elements on speeding behaviour, but it is less clear how universal these effects are. This was the focus of an online questionnaire study for the ERASER ERANET-roads project on self-explaining roads. It was conducted simultaneously in 6 European countries (N=307): Austria, Germany, the Netherlands, Great Britain, Ireland and Sweden. In total, 24 pictures of rural roads were presented; each a different combination of road width, separation of driving direction, vegetation of the roadside environment and the number of lanes per direction. Participants indicated their own driving speed as well as a safe speed limit on these roads. Results indicated that there are particular road features whose effects could be considered relatively self-explaining in the purest sense as they are similar for all countries (road width and vegetation). Effects of other road features, (lanes and type of separation) differed per country. This implies that extra communication (e.g. in an information campaign) or complementing roads with more self-explaining features, might enhance the desired speed behaviour.
Also in this project, a system for automated video analysis was used to collect the actual driving speed data for validation purposes. Two sites at a 2+1 road in southern Sweden were filmed using several cameras in order to be able to cover longer sections (200 and 100 m respectively). The video analysis system was adjusted so that the data from each individual camera could be connected into continuous speed profiles. Comparison with the questionnaire answers for the same road design showed good correspondence between the stated and actual driving speeds.
