Critical Transit Infrastructure in Smart Cities and Urban Air Quality: A Multi-City Seasonal Comparison of Ridership and PM2.5

TL;DR

This study creates a multi-source dataset linking transit ridership and PM2.5 air quality across four U.S. cities, revealing seasonal and city-specific variations and emphasizing integrated monitoring for sustainable urban health.

Contribution

It develops a transparent, scalable framework for combining transit and air quality data, enabling cross-city comparisons and supporting smart-city resilience strategies.

Findings

Pronounced structural differences in transit and air quality across cities.

Seasonal shifts in ridership and PM2.5 vary by urban context.

Mobility-PM2.5 relationships are city- and season-dependent, influenced by baseline effects.

Abstract

Public transit is a critical component of urban mobility and equity, yet mobility and air-quality linkages are rarely operationalized in reproducible smart-city analytics workflows. This study develops a transparent, multi-source monitoring dataset that integrates agency-reported transit ridership with ambient fine particulate matter PM2.5 from the U.S. EPA Air Quality System (AQS) for four U.S. metropolitan areas - New York City, Chicago, Las Vegas, and Phoenix, using two seasonal snapshots (March and October 2024). We harmonize heterogeneous ridership feeds (daily and stop-level) to monthly system totals and pair them with monthly mean PM2.5 , reporting both absolute and per-capita metrics to enable cross-city comparability. Results show pronounced structural differences in transit scale and intensity, with consistent seasonal shifts in both ridership and PM2.5 that vary by urban context. A set of lightweight regression specifications is used as a descriptive sensitivity analysis, indicating that apparent mobility-PM2.5 relationships are not uniform across cities or seasons and are strongly shaped by baseline city effects. Overall, the paper positions integrated mobility and environment monitoring as a practical smart-city capability, offering a scalable framework for tracking infrastructure utilization alongside exposure-relevant air-quality indicators to support sustainable communities and public-health-aware urban resilience.