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

Heavy-duty Truck Emissions in the South Coast Air Basin of California

California and Federal emissions regulations for 2007 and newer heavy-duty diesel engines require an order of magnitude reduction in particulate matter and oxides of nitrogen spurring the introduction of new aftertreatment systems. Since 2008 four emission measurement campaigns have been conducted at a Port of Los Angeles location and an inland weigh station in the South Coast Air Basin of California. Fuel specific oxides of nitrogen emissions at the Port have decreased 12% since 2010 while infrared opacity (a measure of particulate matter) remained low, showing no diesel particulate filter deterioration. The weigh station truck’s fuel specific oxides of nitrogen emission reductions since 2010 (18.5%) almost double the previous three year’s reductions and are the result of new trucks using selective catalytic reduction systems. Trucks at the weigh station equipped with these systems have a skewed oxides of nitrogen emissions distribution (half of the emissions were from 6% of the measurements) and had significantly lower emissions than similarly equipped Port trucks. Infrared thermographs of truck exhaust pipes revealed that the mean temperature observed at the weigh station (225 ± 4.5°C) was 70ºC higher than for Port trucks, suggesting that the catalytic aftertreatment systems on trucks at our Port site were below minimum operating temperatures

Multi-species Remote Sensing of Vehicle Emissions on Sherman Way in Van Nuys California

As part of the 2010 Van Nuys tunnel study, researchers from the University of Denver measured on-road fuel-specific light-duty vehicle emissions from nearly 13,000 vehicles on Sherman Way (0.4 miles west of the tunnel) in Van Nuys, CA with its multi-species FEAT remote sensor a week ahead of the tunnel measurements. The remote sensing mean gram per kilogram carbon monoxide (CO), hydrocarbons (HC), and oxides of nitrogen (NOx) measurements are 8.9% lower, 41%, and 24% higher than the tunnel measurements respectively. The remote sensing CO/NOx and HC/NOx mass ratios are 28% lower and 20% higher than the comparable tunnel ratios. Comparisons with the historical tunnel measurements show large reductions in CO, HC and NOx over the past 23 years, but little change in the HC/NOx mass ratio since 1995. The fleet CO and HC emissions are increasingly dominated by a few gross emitters with more than a third of the total emissions being contributed by less than 1% of the fleet. An example of this is a 1995 vehicle measured 3 times with an average HC emission of 419g/kg fuel (2-stroke snowmobiles average 475g/kg fuel) responsible for 4% of the total HC emissions. The 2008 economic downturn dramatically reduced the number of new vehicles entering the fleet, leading to an age increase (\u3e1 model year) of the Sherman Way fleet which has increased the fleet’s ammonia (NH3) emissions. The mean NH3 levels appear little changed from previous measurements collected in the Van Nuys tunnel in 1993. Comparisons between weekdays and weekend data show few fleet differences although the fraction of light-duty diesel vehicles decreased from the weekday (1.7%) to Saturday (1.2%) and Sunday (0.6%)

Emission Changes Resulting from the San Pedro Bay, California Ports Truck Retirement Program

Recent US EPA emissions regulations have resulted in lower emissions of particulate matter and oxides of nitrogen from heavy-duty diesel trucks. To accelerate fleet turnover the State of California in 2008 along with the Ports of Los Angeles and Long Beach (San Pedro Bay Ports) in 2006 passed regulations establishing timelines forcing the retirement of older diesel trucks. On-road emissions measurements of heavy-duty diesel trucks were collected over a three-year period, beginning in 2008, at a Port of Los Angeles location and an inland weigh station on the Riverside freeway (CA SR91). At the Port location the mean fleet age decreased from 12.7 years in April of 2008 to 2.5 years in May of 2010 with significant reductions in carbon monoxide (30%), oxides of nitrogen (48%) and infrared opacity (a measure of particulate matter, 54%). We also observed a twenty-fold increase in ammonia emissions as a result of new, stoichiometrically combusted, liquefied natural gas powered trucks. These results compare with changes at our inland site where the average ages were 7.9 years in April of 2008 and 8.3 years in April of 2010, with only small reductions in oxides of nitrogen (10%) being statistically significant. Both locations have experienced significant increases in nitrogen dioxide emissions from new trucks equipped with diesel particle filters; raising the mean nitrogen dioxide to oxides of nitrogen ratios from less than 10% to more than 30% at the Riverside freeway location