Doh-Won Lee

On-road Heavy-duty Vehicle Emissions Monitoring System

The introduction of particulate and oxides of nitrogen (NOx) after-treatment controls on heavy-duty vehicles has spurred the need for fleet emissions data to monitor their reliability and effectiveness. The University of Denver has developed a new method for rapidly measuring heavy-duty vehicles for gaseous and particulate fuel specific emissions. The method was recently used to collect 3088 measurements at a Port of Los Angeles location and a weigh station on I-5 in northern California. The weigh station NOx emissions for 2014 models are 73% lower than 2010 models (3.8 vs 13.9 gNOx/kg of fuel) and look to continue to decrease with newer models. The Port site has a heavy-duty fleet that has been entirely equipped with diesel particulate filters since 2010. Total particulate mass and black carbon measurements showed that only 3% of the Port vehicles measured exceed expected emission limits with mean gPM/kg of fuel emissions of 0.031 ± 0.007 and mean gBC/kg of fuel emissions of 0.020 ± 0.003. Mean particulate emissions were higher for the older weigh station fleet but 2011 and newer trucks gPM/kg of fuel emissions were nevertheless more than a factor of 30 lower than the means for pre-DPF (2007 and older) model years.

Evaluation of In-Use Emissions from Refuse Trucks

The main objective of this paper is to evaluate the in-use emissions from heavy-duty diesel refuse trucks during their different modes of operation. The paper presents a collection of field emissions data from a sample of three side-loader refuse trucks in El Paso, Texas. The gaseous (carbon dioxide, carbon monoxide, nitrogen oxides, and total hydrocarbons) and particulate matter emissions rates were measured by means of two portable emissions measurement systems. The collected emissions data were divided into four distinct operation modes: city driving, highway driving, trash collection, and landfill activities. Emissions data were analyzed and operational and emissions characteristics of each mode were investigated. The trash collection and highway driving were found to produce the highest amount of pollutants for a side-loader refuse truck. It was also observed that while most of the highway driving occurred outside the boundary of the residential areas, almost all the trash collection activities occurred in residential areas. An in-depth analysis on trash collection mode was performed to investigate further the emissions characteristics of trash collection modes. The results of these studies will be used to evaluate the cost-effectiveness of using landfill gas generated at landfills as a liquid natural gas fuel source for refuse trucks.