Attitude vs. infrastructure: Influences on the intention to overtake bicycle riders

The Theory of Planned Behavior (Ajzen, 1991) has recently gained some heightened attention in the traffic safety community in predicting risky behavior. On the other hand, infrastructure layout has often been shown to influence road user behavior in direct ways in traffic observations. In an online survey, 108 holders (81% female) of a valid car-driving license reported on their attitude, social norms, and perceived behavioral control towards overtaking bicycle riders with a smaller than legal margin. Additionally, they rated their willingness to overtake a bicycle rider as well as perceived risk for six traffic sketches. In these sketches, infrastructure layout was systematically varied on two dimensions: (1) streets with or without a center-line between directions of travel and (2) streets marked with either a cycle lane, an advisory lane for bicycle riders or none of these. A repeated measures ANOVA with center line and cycling street markings as independent variables and attitude, social norms, and perceived behavioral control as covariates showed that intention to overtake was only influenced by street markings and the interaction of attitude and street markings, showing that intention to overtake was higher with markings than without, and even higher when attitude towards illegally small distances to overtake was more positive. Ratings of risk while overtaking were only influenced by street markings, showing that ratings of risk were lower for any of the marked designs than those without. Data analysis suggests that personal motivations play a far less important role in the intention to overtake bicycle riders with a non-safe distance than infrastructure designs do. Even the judgement of risk for a given situation seems to be influenced by some markings on the street but not by personal motivations.