Do supplementary signs distract the driver?

• The effect of new advertisement on German highways on driving safety was evaluated.
• Three experimental setups from basic psychology were used.
• Results were confirmed in a study in the driving simulator.
• No negative effects of the new signs on driving safety could be found.
• Drivers avoid distraction by the new signs through efficient attentional strategies.

In 2005, the regulation of signage on German highways was changed and now allows supplementary signs. These signs are installed below direction signs and inform about the services offered on motorway service areas. Being advertisement, the supplementary signs bear the risk to distract drivers looking for directional information. To study the influence of supplementary signs, four experiments (N = 30) were conducted. Experiment 1 used the phenomenon of change blindness as an indicator for the allocation of attention. It could be shown that drivers searching for a specific direction direct nearly no attention to the supplementary signs. In experiment 2 and 3, the influence of the supplementary signs on perceptional threshold for directional information and on self-chosen perception times was measured. Neither the perceptional threshold nor perception times freely chosen by the participants were negatively affected by the supplementary signs. The last experiment analyzed the influence of supplementary signs on driver reaction in a critical driving situation in a driving simulator study. Here, supplementary signs had no negative impact on collision rate and reaction time. Based on the results, it is concluded that drivers use effective attentional strategies while searching for directional information. In the experiments no negative effects of the supplementary signs could be found.