Air Pollution Impacts of Shifting San Pedro Bay Ports Freight from Truck to Rail in Southern California

Escalating concerns about air quality in Southern California have led authorities of the Ports of Los Angeles and Long Beach, also known as the San Pedro Bay Ports (SPBP), to consider and adopt a number of emission mitigation measures. One possibility is to shift to trains some of the containers currently transported by drayage trucks. This alternative is attractive because it would decrease congestion and air pollution on the main freeways (I-710 and I-110) and arterials that serve the SPBP. In addition, it would increase road safety along the busy Alameda freight corridor between the SBBP and downtown Los Angeles. One drawback would be an increase in pollutant emissions from train operations in the Alameda corridor, but trains tend to pollute less than trucks per ton-mile and new federal regulations are tightening the emission standards for diesel locomotives. The goal of this paper is to quantify the net impact of such a modal shift on the emissions of PM and NOx, which are the two air pollutants of most concern in the SPBP area. Our analysis relies on microscopic simulation to better capture emissions resulting from stop-and-go traffic on the freeways serving the SPBP. We find that emissions of both NOX and PM2.5 can be significantly reduced by switching from drayage trucks to trains. This suggests that modal shift should be encouraged, especially if there is unused 16 train capacity, and as long as it does not conflict with the shippers’ interests.