Joint Model of Sustainable Mode Choice for Commute, Shift Potential and Alternative Mode Chosen

Rising traffic congestion and severe air pollution in urban areas have led policymakers to find appropriate strategies to encourage the use of sustainable modes. In this context, this paper investigates three choice dimensions related to the work commute travel: (i) Whether and to what extent are sustainable modes considered? (ii) What factors influence the propensity to shift from the primary work commute mode? (iii) Which mode is most likely to be chosen conditional on the decision to shift? These dimensions are analyzed using data of workers from Chennai, India. As the three choices of an individual may be correlated and mutually endogenous because of common and persistent psychological attributes and modal service characteristics, they are modeled using a multi-dimensional probit model. The results show significant evidence of endogeneity, state-dependence, and unobserved correlation across these dimensions leading to significant improvement in fit measures. The results show that perceptions of walkability and environmental impacts of travel modes affect only the consideration of sustainable modes, while vehicle ownership and accessibility to transit affect all three dimensions. Four different behavioral motivations for the decision to shift from the usual mode: dissatisfaction with service attributes, activity constraints, multimodal travel pattern, and inertia, were identified. The mode to which shift occurs is influenced by household vehicle fleet (number and type), exclusive availability to the given decision-maker, and work distance. The insights from this study can be used to identify suitable factors and frame policies to promote sustainable mode choice at various levels.