Trends in Heavy-Duty Diesel Emissions and Analyses of Colorado\u27s Light-Duty Vehicle Inspection and Maintenance Program

Emission trends are reported and discussed resulting from the multi-year study of Heavy-Duty Diesel Vehicles (HDDV) at the Port of Los Angeles and at a weigh station in Peralta also in the L.A. basin. Remote sensing data were also collected from the Port of Houston and compared to the data from California. As part of San Pedro Bay Ports Clean Air Action Plan (CAAP) to fast track the turnover rate of cleaner trucks, many truck operators have been subject to modifying their trucks, or have purchased new trucks, with more advanced control technologies to reduce exhaust particulate matter (PM) and oxides of nitrogen (NOx). These advanced control technologies have been proven to effectively reduce these emissions but have some unwanted effects such as increasing the NO2/NO ratio in diesel exhaust which has the potential to increase ground level ozone. Ammonia (NH3) was found to be an unexpected product from one of the new control technologies as almost all the NOx is reduced to NH3. In addition to the HDDV comparison, two years worth of emissions records from Colorado\u27s light-duty fleet Inspection Maintenance (I/M) program were matched and compared with the on-road measurements. This analysis shows that switching to an On-Board Diagnostics only program would cost 5-8 times as much as the currently used dynamometer tests and achieve only a fraction of emissions benefit from the current I/M program