Phoenix Regional Heat and Air Quality Knowledge Repository

Public transit systems have been identified as a critical component to reducing energy use and greenhouse gas emissions associated with the transportation sector to mitigate future climate change impacts. A unique aspect of public transit is its use almost always necessitates environmental exposure and the design of these systems directly influences rider exposure via rider ingress, egress, and waiting. There is a tension between policies and programs which promote transit use to combat climate change and the potential impact an uncertain climate future may have on transit riders.

In the American Southwest, extreme heat events, a known public health threat, are projected to increase between 150 and 840% over the next decade, and may be a health hazard for transit riders. There are opportunities to incorporate rider health risks in the overall planning process and develop alternative transit schedules during extreme heat events to minimize these risks. Using Los Angeles Metro as a case studies, we show that existing transit vehicles can be reallocated across the system to significantly reduce exposure for riders who are more vulnerable to heat while maintaining a minimum level of service across the system. As cities continue to invest in public transit it is critical for them to understand transit use as an exposure pathway for riders and to develop strategies to mitigate potential health risks.

The forthcoming century will see cities exposed to temperature rises from urbanisation as well as greenhouse gas induced radiative forcing. Increasing levels of urban heat will have a direct impact upon the people living in cities in terms of health, but will also have an indirect effect by impacting upon the critical infrastructure networks of the city itself (e.g., ICT, transport and energy). Some infrastructures are more resistant than others, but there is a growing reliance on the energy network to provide the power for all of our future critical infrastructure networks. Unfortunately, the energy network is far from resilient from the effects of urban heat and is set to face a perfect storm of increasing temperatures and loadings as demand increases for air conditioning, refrigeration, an electrified transport network and a high-speed ICT network. The result is that any failure on the energy network could quickly cascade across much of our critical infrastructure. System vulnerabilities will become increasingly apparent as the impacts of climate change begin to manifest and this paper calls for interdisciplinary action outlining the need for high resolution monitoring and modelling of the impact of urban heat on infrastructure.