Climate Change

Bus and Rail Network Design and Exposure to Extreme Heat

We have developed a framework for assessing exposure to environmental conditions (e.g., extreme heat, precipitation, or cold) based on network analyses of parcels, transit networks, and transit schedules. We simulate for every residential parcel in a city how long they are exposed based on their walking times to and from transit and their waiting times at transit. Our results show that, in the case of Southwest U.S. cities, that when temperature is highest (midday), exposure is greatest due to lower headways at offpeak times. We overlay social vulnerability indices to show which neighborhoods are at greatest risk. With this information we are able to direct transit agencies towards strategic investments in schedule changes, public outreach, and communication of transit schedules to reduce these vulnerabilities.

Heat Exposure and Transit Use: Travel Behavior and Infrastructure

ASU Report No. ASU-SSEBE-CESEM-2017-CPR-001

Public transit necessitates environmental exposure and there is increasing recognition that in a future with hotter temperatures new strategies are needed to protect passengers. Arizona State University’s Spring 2017 Urban Infrastructure Anatomy course assessed travel behavior, public transit stop design, and heat exposure to develop recommendations for mitigating heat exposure. Travel surveys, analysis of infrastructure characteristics, and thermal imaging were used to assess exposure. A suite of mitigation strategies was developed from a literature review, conversations with experts, and review of other transit systems. Focusing on neighborhoods in Tempe, Arizona, strategies are developed for protecting future riders from negative health outcomes.

Transit System Design and Vulnerability of Riders to Heat

Journal of Transportation and Health, 2017, 4, pp. 216-225, doi: 10.1016/j.jth.2016.07.005

In the United States public transit utilization has increased significantly in the last decade and is considered a critical component in reducing energy use and greenhouse gas emissions in urban areas. Despite public transit׳s climate change mitigation potential, the use of transit necessitates environmental exposure which may be a health hazard during periods of extreme heat. Transit system design, which includes stop location and schedules, is shown to contribute to environmental exposure resulting from access and waiting. Using Los Angeles Metro (Los Angeles County, CA) and Valley Metro (Maricopa County, AZ) as case studies of systems operating in extreme heat conditions, the research demonstrates how system design contributes to heat exposure times that vary significantly between neighborhoods. Household level access (walking) time estimates are developed using a shortest path algorithm to nearby transit stops. Waiting time estimates for individual transit stops are derived from published transit schedules and on-board survey responses. The results show that transit users from areas with low residential density, limited high capacity roadways and irregular street networks, and not located along direct paths between major activity centers are likely to experience prolonged access and/or waiting times. Public transit may help mitigate climate change impacts but transit proponents, agencies and planners should be cognizant of the impact an uncertain climate future may have on a growing base of transit riders. These insights can allow us to proactively govern and adapt transit systems to protect people from a growing health concern.

Frameworks for Assessing the Vulnerability of U.S. Rail Systems to Flooding and Extreme Heat

Arizona State University Report No. ASU-SSEBE-CESEM-2015-RPR-001

Recent climatic trends show more flooding and extreme heat events and in the future transportation infrastructure may be susceptible to more frequent and intense environmental perturbations. Our transportation systems have largely been designed to withstand historical weather events, for example, floods that occur at an intensity that is experience once every 100 years, and there is evidence that these events are expected become more frequent. There are increasing efforts to better understand the impacts of climate change on transportation infrastructure. An abundance of new research is emerging to study various aspects of climate change on transportation systems. Much of this research is focused on roadway networks and reliable automobile travel. We explore how flooding and extreme heat might impact passenger rail systems in the Northeast and Southwest U.S..