Joint Models for Consideration of Public Transit and Mode Choice for Work Commute

The mode share of public transit has been decreasing in many Indian cities, while the ownership and usage of personal vehicles continue to grow. It is important to understand the reason behind this decline in transit ridership and frame policies to reverse this trend. Traditional mode choice models assume that all the modes are considered in the choice set while making a decision, which may not be realistic due to the following reasons. Individuals may not consider some modes due to the unavailability, lack of information, or infeasibility, or incompatibility with their travel and activity patterns. By ignoring this consideration process and assuming that all modes are available can lead to mis-specified models and erroneous policy evaluations. Thus, it is important to model both consideration and mode choice outcomes jointly. Accordingly, the main objective of this paper is to develop a joint model for three inter-related choice dimensions: (1) the consideration of bus, (2) the consideration of train, and (3) the primary mode for the home to work commute. These models are estimated using data from a sample of workers in Chennai city and the key explanatory variables influencing them are investigated. A positive correlation between the consideration of bus and train is found. The results also show that consideration of public transport modes influences the mode choice as expected. Furthermore, the coefficient of (log of) consideration probability on choice utility is significantly different from one (an assumption in many implicit availability/perception models). Also, some of the factors affected both the consideration and choice decisions, thus providing evidence that there is a partial (not complete) mediation effect of consideration on choice. Comparison with alternative models shows that neglecting these effects of consideration on choice can lead to biased coefficients, erroneous inferences, and poor model fit. The degree of vehicle availability and accessibility to transit stations exhibit varied effects in the choice of bus and train modes. In addition, their influence differs between the consideration and choice stages. The findings from this study could help decision-makers in developing separate policies for augmenting the consideration of public transit versus those that aim to retain or increase market shares.