Measuring transit riders’ heat exposure and mitigation during the 2021 Vancouver heatwave

Previous research on transit riders’ vulnerability to heat often relies on coarse approximations of thermal comfort or unintuitive measures of exposure. Moreover, despite the potential for shade and transit shelters to mitigate heat, little research has considered their availability throughout transit journeys. Using the 2021 extreme heat event in Vancouver, BC, Canada as a case study, we integrate high-resolution urban microclimate models and transit trip simulations to assess the socio-spatial patterns of risk faced by transit riders. We propose four intuitive measures that describe what residents departing from different neighbourhoods can expect in terms of potential exposure and mitigation availability, on average, when travelling anywhere across the transit network. We leverage these metrics for social equity analysis. We find that significantly larger shares of marginalized populations live in neighbourhoods with the highest exposure and lowest levels of mitigation, highlighting the urgent need for equity-focused climate adaptation policies in transit systems.