Riders on the storm: Exploring weather and seasonality effects on commute mode choice in Chicago

This paper separately analyzes the impacts of weather and seasonality on commute mode choice using a stated-preference (SP) survey. The study's twin objectives include quantifying the relative attractiveness of a flexible transit mode under adverse weather and analyzing the heterogenous impacts of seasonality and weather on different segments of the population. The survey was implemented during summer and winter months to analyze the impact of seasonality on commute mode choice. To analyze the impact of weather on commute mode choice, the survey randomly assigns respondents to a good or bad weather scenario. The three SP mode choice options are fixed-route transit, personal car, and a hypothetical flexible transit mode. The flexible transit mode allows travelers to wait for a transit vehicle at their origin point – an especially attractive feature on cold and/or snowy/rainy days. However, like with existing dial-a-ride services, travelers using the flexible transit service may experience detours between their pickup and drop-off locations. Several panel mixed-logit choice models that incorporate weather and seasonality were estimated using the SP survey data. The panel mixed-logit model form captures taste heterogeneity across respondents and correlation across multiple SP choice experiments from a single respondent. Model estimation results indicate that relative to good weather, summer days, respondents were significantly more likely to choose traditional and flexible transit on good weather, winter days, and flexible transit on bad weather, winter days. Furthermore, the results show that the impacts of weather and seasonality on commute mode choice vary across the population. Most of the respondents had a lower (higher) propensity to choose the car (flexible transit) mode under bad weather than good weather. Conversely, car commuters, bicycle commuters, and baby boomers had a much higher propensity to choose the car mode under bad weather than good weather. Additionally, the results show that millennials had a much lower propensity to choose the car mode in the winter than the summer, whereas seasonality had little impact on the propensity of non-millennials to choose the car mode. The paper discusses the implications of these findings on the design of transit, flexible transit, and emerging mobility services, as well as the management of transportation systems and dissemination of information regarding alternative transport modes during adverse weather events.