MPC Research Reports
Report Details

Title:	Impacts of Area-Wide Air Pollution on Multimodal Traffic Volumes in Utah
Authors:	Patrick A. Singleton, Prachanda Tiwari, and Keunhyun Park
University:	Utah State University
Publication Date:	Sep 2024
Report #:	MPC-24-554
Project #:	MPC-662

Abstract

During area-wide episodes of poor air quality, people may reduce their transportation-related emissions by driving less, reducing their exposure to emissions by walking/bicycling less, or going about their lives as usual. These three reactions have different consequences for transportation, health, and the environment. This study investigated the aggregate effects of air pollution on multimodal traffic volumes by comparing associations of the daily air quality index with pedestrian and automobile traffic volumes (collected at many different locations) and system-wide bus/rail ridership over a two-year period in two regions of Utah, United States. We used multilevel modeling to measure how these relationships differ by mode and across locations, while controlling for weather and investigating built/social environmental characteristics. Overall, we found strong evidence that pedestrian volumes declined by 10% or more, on average, on days where the air quality was "unhealthy for sensitive groups" (orange). There was some evidence that automobile traffic volumes increased on poor air quality days, especially on the way to mountainous recreation areas surrounding urban valleys. Decreases in bus/rail ridership were not statistically significant. Overall, there was more evidence for "risk averse" reactions than for "altruistic" travel behavior changes, suggesting that newer or stronger policies may be needed in order to reduce driving and encourage more sustainable and healthful travel behavior changes in regions when faced with periods of area-wide poor air quality.

How to Cite

Singleton, Patrick A., Prachanda Tiwari, and Keunhyun Park. Impacts of Area-Wide Air Pollution on Multimodal Traffic Volumes in Utah, MPC-24-554. North Dakota State University - Upper Great Plains Transportation Institute, Fargo: Mountain-Plains Consortium, 2024.