Emissions Comparison between Truck and Rail: Case Study of California I-40

A comprehensive goods movement study of the California Interstate 40 corridor (from Barstow to Needles) has recently been completed. This study attempted to characterize goods movement in the region, perform a corridor emissions analysis, and make recommendations in terms of capacity and improvements, as well as economic feasibility of using rail in conjunction with trucks for goods movement. The emissions analysis of goods movement along the I-40 corridor is examined, specifically emissions of carbon monoxide, hydrocarbons, nitrogen oxides (NOx), and particulate matter associated with both truck and rail traffic. Heavy-duty diesel truck emissions are estimated using truck activity data recorded along the corridor. A unique methodology is used to calculate these truck emissions, incorporating road grade factors and determining engine load on a link-by-link basis. These emissions are then compared with the emissions associated with freight trains that travel along this I-40 corridor. On the basis of current (1994) truck and rail volumes, it was found that goods moved by rail produces lower emissions, except for NO_x, which is slightly higher for rail. The factor decrease of other pollutants ranges from 2.49 to 8.50, which is consistent with other recent studies. Given the amount of pollutants produced by trucks, shifting some of the freight from trucks to rail with a greater emphasis on intermodal business should reduce the total freight emissions along the I-40 corridor.