Where Sustainable Transportation Becomes Vulnerable: Weather, Last-Mile Access, and Mode Choice

Sustainable transportation systems can remain operational while becoming functionally vulnerable when access to them deteriorates. We distinguish two dimensions of transport resilience—operational resilience, the continued running of the main transport services, and functional accessibility resilience, users’ capacity to reach them—and locate weather-induced vulnerability in the latter. We focus on weather-induced last-mile vulnerability and examine how adverse weather alters mode choice. Drawing on a discrete choice experiment with 760 respondents in Portland, we estimate a mixed logit model capturing the effects of rain. The results reveal that rain significantly increases the disutility of travel time, intensifies the burden of last-mile walking, and strongly discourages bicycle use. In contrast, no statistically significant additional average disutility is found for transit itself. Marginal willingness to pay for travel time reduction increases from $1.53 per minute in sunny weather to $2.54 in rainy weather, while the average predicted probability of choosing car rises from 34.9% to 54.4%. These findings suggest that weather sensitivity is driven less by main transit services than by the surrounding access conditions and active travel links. The study contributes to transportation resilience research by showing that strengthening last-mile access under adverse weather is essential for sustaining low-carbon mobility choices.