A Spatial-Temporal Analysis of Travel Time Gap and Inequality Between Transit and Vehicles

The increasing car usage has led to environmental issues. Public transit offers an affordable, eco-friendly alternative. Nevertheless, the proliferation of public transit ridership is encumbered by multifarious factors, such as fixed schedules, limited routes, sparse population density, and commuter perceptions. Among these, the travel time gap between transit and personal vehicle act as an impediment to broader transit adoption. In this study, we addressed two research questions: (1) How does the travel time gap between public transit and personal vehicles evolve over? (2) Is there a presence of inequality in the travel time gap, and how does its temporal trend unfold?

This analysis was stratified by urban classifications, disadvantaged communities (DAC), and states. We utilized the data from the Census Transportation Planning Program (CTPP) dataset, specifically the origin-destination (OD) data at the Census Tract Level. The travel time gap for each OD pair is established as a variable based on data at Census Tract level, represented by the ratio of public transit travel time over private vehicle travel time. Inequality pertains to the uneven distribution of this travel time gap, which reflects the combined attributes of a specific region. Consequently, the inequality of travel time gap is defined as a county-level variable. This variable is constructed as a composite metric involving the mean and standard deviation of the travel time gap within each county, proposed by Pandey et al.

This preliminary investigation focuses on five northeastern U.S. states: New York, Connecticut, Pennsylvania, Delaware, and Massachusetts. We utilize two series of CTPP data spanning 2010 (based on the 2006-2010 American Community Survey) and 2016 (based on the 2012-2016 American Community Survey). Exclusions are made for OD pairs with missing transit or private vehicle travel time data, resulting in a dataset of 3,230 OD pairs.

Our analysis reveals a slight increase in travel time gap from 2010 to 2016 across all states, except Connecticut. The average travel time gap was 1.96 in 2010 and 2.12 in 2016. The median increase across states ranged from 42% to 55%. Specifically, within New York State's urban DAC, there was a significant rise in mean travel time gap from 2.45 in 2010 to 2.70 in 2016 (p-value=0.09). A similar trend was observed in Delaware, where the gap increased from 1.59 to 3.23 (p-value=0.06). Additionally, in non-DAC urban regions of Massachusetts, although the travel time gap's absolute value may lack statistical significance, their inequality showed a substantial 33% increase from 2010 to 2016 (p-value = 0.03).

The findings suggest that while travel time gap between transit and personal vehicles may not increase significantly over the years, the inequality might increase in certain regions. This phenomenon could be attributed to disproportionate enhancements in public transit provisions across regions. Scrutinizing these inequalities can provide valuable insights aimed at fostering equitable advancements in transportation infrastructure.

Reference:

Pandey, B., Brelsford, C., & Seto, K. C. (2022). Infrastructure inequality is a characteristic of urbanization. Proceedings of the National Academy of Sciences, 119(15), e2119890119. https://doi.org/10.1073/pnas.2119890119