The conditional effects of social influence in transportation mode choice

Recent research suggests that an individual's transportation mode choice is partially influenced by the mode choice of other people in their social network. This paper advances this basic idea by testing the hypothesis that the extent of social influence is conditional on external context factors such as commute characteristics. Through an online survey of students at the University of California, Davis, we collected information about students' transportation decisions for campus travel and their social networks. For each participant as an ego, we gathered information about their ego-network including up to five social contacts or alters. A series of complementary statistical models find the strength of social influence is lower for those with longer commute distances where biking is more costly than driving or taking the bus, and is also lower at distances where walking has higher utility than biking. Social influence is most important when the external commute characteristics entail relatively equal travel costs for different modes. As social influence and other social processes are evaluated as potential policy instruments, these and other heterogeneous effects should be taken into account.