I was interviewed for an article in the Christian Science Monitor about the impacts of the COVID pandemic on public transit. The reporter did a nice job of summarizing my thoughts on the role of public transit at this moment in history:
Self-driving cars offer some hope to reduce pollution in the near future. Yet progress has been slow, says Professor Miller, and autonomous vehicles aren’t likely to enter city streets within the decade. Even at their electrified best, he says, cars are still an inefficient form of transportation, and hence an imperfect solution to the climate crisis.
In his opinion, the moment demands a grand shift in thought. If viewed as a foundational piece of urban infrastructure, public transit could expand this decade and cement a larger role in the transportation ecosystem. Permitting residents a larger menu of options when traveling – say biking, walking, or riding buses or subways – would help conserve city space, lower spending, and protect the environment.
Urban transit took a pandemic wallop. Can it bounce back? Christian Science Monitor, 25 Feb 2021
New paper: Liu L, Miller HJ, Scheff J (2020) The impacts of COVID-19 pandemic on public transit demand in the United States. PLOS ONE 15(11):e0242476. https://doi.org/10.1371/journal.pone.0242476
The COVID-19 pandemic and related restrictions led to major transit demand decline for many public transit systems in the United States. This paper is a systematic analysis of the dynamics and dimensions of this unprecedented decline. Using transit demand data derived from a widely used transit navigation app, we fit logistic functions to model the decline in daily demand and derive key parameters: base value, the apparent minimal level of demand and cliff and base points, representing the initial date when transit demand decline began and the final date when the decline rate attenuated. Regression analyses reveal that communities with higher proportions of essential workers, vulnerable populations (African American, Hispanic, Female, and people over 45 years old), and more coronavirus Google searches tend to maintain higher levels of minimal demand during COVID-19. Approximately half of the agencies experienced their decline before the local spread of COVID-19 likely began; most of these are in the US Midwest. Almost no transit systems finished their decline periods before local community spread. We also compare hourly demand profiles for each system before and during COVID-19 using ordinary Procrustes distance analysis. The results show substantial departures from typical weekday hourly demand profiles. Our results provide insights into public transit as an essential service during a pandemic.
New paper: Lee, J. and Miller, H.J. (2020) “Robust accessibility: Measuring accessibility based on travelers’ heterogeneous strategies for managing travel time uncertainty,” Journal of Transport Geography, 86, 102747.
- We develop an analytical framework for measuring accessibility considering travelers’ heterogeneous safety margin plans and routing strategies under travel time uncertainty.
- We explore how accessibility changes under various safety margin plans and routing strategies.
- We define and measure robust accessibility: geographic areas that are accessible regardless of the safety margin planning and routing strategy.
- Robust accessibility provides a conservative and reasonable view of accessibility under travel time uncertainty.
- We apply our framework to measure the accessibility impacts of new public transit service under travel time uncertainty.
Uncertainties in travel times due to traffic congestion and delay are risks for drivers and public transit users. To avoid undesired consequences such as losing jobs or missing medical appointments, people can manage the risks of missing on-time arrivals to destinations using different strategies, including leaving earlier to create a safety margin and choosing routes that have more reliable rather than fastest travel times. This research develops a general analytical framework for measuring accessibility considering automobile or public transit travelers’ heterogeneous strategies for dealing with travel time uncertainty. To represent different safety margin plans, we use effective travel time (expected time + safety margin), given specified on-time arrival probabilities. Heterogeneity in routing strategy is addressed using different Pareto-optimal routes with two main criteria: faster travel time vs. higher reliability. Based on various safety margin and routing strategy combinations, we examine how accessibility changes under varying safety margin plans and routing strategies. Also, we define and measure robust accessibility: geographic regions that are accessible regardless of the safety margin planning and routing strategy. Robust accessibility can provide a conservative and reasonable view of accessibility under travel time uncertainty. To demonstrate the applicability of the methods, we carry out an empirical study on measuring the impacts of new transit service on healthcare accessibility in a deprived neighborhood in Columbus, Ohio, USA.