Traffic, Air Quality, and Environmental Justice in the South Coast Air Basin During California’s COVID-19 Shutdown

Historically, Southern California suffers from the worst traffic congestion and air quality levels in the country. During the COVID-19 pandemic in 2020, we observed a major reduction in economic and social activities within the region, leading to changes in roadway traffic and air pollution levels in a variety of ways. Within six weeks of the pandemic-induced lockdowns, freeway traffic volume dropped as low as 50%; however, it has since gradually increased back to pre-pandemic levels. The changes in freeway traffic volume have not been uniform across the Southern California region, and neighborhoods with different socio-economic profiles were affected differently. These disparities have brought up environmental justice concerns, particularly for disadvantaged communities that live adjacent to major roadways and warehouse centers. We monitored the changes in vehicle and human activities across communities in Southern California and explored correlations that are useful for developing various mitigation measures at both the local and regional levels. In this study, we go beyond regional analysis and examine the effects of the pandemic on traffic at a transportation corridor and local levels to examine possible equity issues. Results show that, in general, the level of traffic dropped less in disadvantaged neighborhoods during the pandemic. Further, traffic flow rebounded in these neighborhoods faster than in other communities.