Executive Summary

Diesel particulate matter (PM) emissions have been estimated to cause more negative health impacts and premature deaths in New York City than any other US city. Heavy-duty diesel vehicles emit roughly 10 times the number of particles as gasoline passenger cars, and contribute to extremely high ultra-fine particle concentrations near major roadways. Environmental justice concerns are raised because minority and low-income populations are more likely to live in urban areas with high levels of motor vehicle traffic. In NYC, diesel truck traffic on major freeways and Hunts Point Market is believed to be one of the major reasons the Bronx has the highest asthma mortality rates of the five NYC boroughs.

To combat particulate pollution in the region, NYC has taken serious actions to reduce particulate pollution from diesel sources. Through the Clean Fuel Bus Program, NYC Transit has purchased the largest hybrid-diesel electric bus fleet in North America, and by the end of last year, had retrofitted all of the conventional diesel transit buses with diesel particle filters. PLANYC2030 outlines NYC’s air quality goals, including retrofitting heavy-duty diesel vehicles in both public and private fleets.

However, given the complexity (e.g., technical, regulatory, financial, operational factors), size and funding requirement of diesel retrofitting, much research needs to be done to achieve cost-effective clean-up of the existing diesel fleets. In “The Retrofit Puzzle: Optimal Fleet Owner Behavior in the Context of Diesel Retrofit Incentive Programs” (1) an integer program was developed to model profit-maximizing diesel fleet owner behavior when selecting pollution reduction retrofits. Fleet owners acted in the context of potential government programs including various mandates and financial incentives. Fleet size and the miles remaining for each vehicle were treated as fixed and known at the time retrofits are made. Retrofits were assumed to take place in the present, but benefits and costs are distributed over time. The model was intended as a tool both for fleet owners and for government administrators. In this proposal, the model will be expanded to allow for retrofits at multiple stages in time. This enhancement enables the model to develop multi-year strategies for retrofit implementation, a capability that is especially important when changing government regulation and incentives, vehicle availability, new retrofit technologies, or other factors make spacing retrofits out over time the most profitable option. A case study in New York State will be used to demonstrate how a sample fleet owner would respond to various incentives.