How commuters' motivations to drive relate to propensity to carpool: Evidence from the United Kingdom and the United States

This paper examines how commuter motivations to drive relate to propensities to carpool, using two sequential studies: Study 1 determines the key dimensions of commuters' motivations for driving using secondary data (N = 432) from staff and postgraduate student commuters at a United Kingdom university. We code the contents of the respondents' self-reported reasons for driving (i.e. the instrumental rationalities attributed to driving with respect to varying purposes) to identify keywords representing motivation to drive; we then analyse the keyword data using multidimensional scaling (MDS). Study 2 examines how the dimensions discovered through study 1 relate to propensity to carpool, using structural equation modelling (SEM). Data for Study 2 are the survey responses of commuters (N = 1028) based in the United States. The MDS reveals four key dimensions of motivation to drive. These capture instrumental rationalities for driving within four situational domains which we term: (1) Family; (2) Public transport impractical changes; (3) Rigid schedule; and (4) Non-urban areas. The SEM results show that the regression coefficients on propensity to carpool of Public transport impractical changes and Rigid schedule are significant and negative; the Family domain has a positive but non-significant regression coefficient. Regarding demographics, men's mean values on all four domain variables are significantly higher than those for women, except for the Family domain where the mean value for women is higher; meanwhile, age predicts decreasing propensity to carpool. Additionally, the situational domains of Public transport impractical changes, Rigid schedule and Non-urban areas significantly positively correlate. Consequently, overall, the results imply that addressing commuters' instrumental rationalities for driving, namely increasing schedule flexibility and providing more direct or quicker public transport, could indirectly encourage commuters to carpool. The study makes an original contribution by estimating the causal relationship between commuters' motivation to drive and propensity to carpool.