Although speed limits are indicated by road signs, road users are not always aware, while driving, of the actual speed limit on a given road segment. The Flemish Roads and Traffic Agency developed additional road markingsin order to support driver decisions on speed on 70 km/h roads in Flanders-Belgium. In this paper the results are presented of two evaluation studies, both a field study and a simulator study, on the effects of the additional road markings on speed behavior. The results of the field study show a tendency towards an increase in the mean speed after implementing the additional road markings. However, the results of the simulator study, with slightly different stimuli, indicate no effect on speed behavior due to the measure. Nevertheless an effect on lateral position was noticed, showingat least some effect of the markings. The role of conspicuity of design elements and expectations towards traffic environments is discussed and some possible explanations for the results are given. Both studies illustratewell some strengths and weaknesses of observational field studies compared to experimental simulator studies. A widespread introduction of the investigated additional markings is not recommended.
Abstract