A joint behavioral choice model of carpool formation and frequency

The future of transportation is often characterized by a vision of shared mobility in which multiple individuals ride in the same vehicle together. The most prevalent form of such shared personal mobility is carpooling. Despite decades of efforts to increase carpool mode shares, the share of carpooling for most travel, and especially work travel, has decreased. There is a need for a deeper understanding of the phenomenon and the drivers that influence carpool choice behavior. To this end, this paper presents an examination of carpool choice behavior with a focus on three critical dimensions of interest: frequency of carpooling, choice of companion for carpooling, and the choice of platform or method for making the carpool arrangement. Using a novel data set derived from a survey of commuters, this paper presents a simultaneous equations model of carpool frequency, companion, and formation method with a view to investigate the carpool choice phenomenon in a more holistic behavioral framework that incorporates a multitude of critical carpool choice dimensions. Results show that individuals do not embrace carpooling with strangers and do not use formal carpool programs to arrange their carpool arrangements. Model results show that a host of socio-demographics and built environment and workplace characteristics affect all three dimensions of carpool behavior. Insights from this study would help in identifying policies and technological platforms that would promote carpooling for disparate population subgroups.