Cost-effectiveness of emissions control strategies for transit buses: The role of photochemical pollutants

The authors extend a previous cost-effectiveness analysis of methanol vs. other means of controlling emissions from urban transit buses by developing a method to incorporate their effects on two endproduct pollutants: ozone and nitrogen dioxide. Using published simulation results from an airshed grid model of ozone formation, they find that the measures we consider have varying effects on ozone at 23 sites in the Los Angeles air basin. The effects are offsetting, leading to a negligible net effect when aggregated across the basin’s population; this is true assuming either that damage is proportional to concentration times population exposed, or that damage is represented by nonlinear concentration-response functions for specific health conditions. In contrast, either low-aromatic diesel fuel or methanol would lower ambient concentrations of nitrogen dioxide enough, relative to the federal or California ambient standard, to significantly affect cost-effectiveness comparisons.