Multispecies remote sensing measurements of vehicle emissions on Sherman Way in Van Nuys, California

Abstract

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, California, with its multispecies Fuel Efficiency Automobile Test (FEAT) remote sensor a week ahead of the tunnel measurements. The remote sensing mean gram per kilogram carbon monoxide (CO), hydrocarbon (HC), and oxide of nitrogen (NO x ) measurements are 8.9% lower, 41% higher, and 24% higher than the tunnel measurements, respectively. The remote sensing CO/NO x and HC/NO x 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 NO x over the past 23 yr, but little change in the HC/NO x 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 three times with an average HC emission of 419 g/kg fuel (twostroke snowmobiles average 475 g/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 (>1 model year) of the Sherman Way fleet that has increased the fleet's ammonia (NH 3 ) emissions. The mean NH 3 levels appear little changed from previous measurements collected in the Van Nuys tunnel in 1993. Comparisons between weekday 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%).Implications: On-road remote sensing emission measurements of light-duty vehicles on Sherman Way in Van Nuys, California, show large historical emission reductions for CO and HC emissions despite an older fleet arising from the 2008 economic downturn. Fleet CO and HC emissions are increasingly dominated by a few gross emitters, with a single 1995 vehicle measured being responsible for 4% of the entire fleet's HC emissions. Finding and repairing and/or scrapping as little as 2% of the fleet would reduce on-road tailpipe emissions by as much as 50%. Ammonia emissions have locally increased with the increasing fleet age.

Comparison of the MOVES2010a, MOBILE6.2, and EMFAC2007 mobile source emission models with on-road traffic tunnel and remote sensing measurements

“…Although California light-duty gasoline vehicle NO x standards were about 25% lower during most of the decade prior to 1994, the contemporary contributions of this portion of the fleet are likely related to emissions of high emitters rather than the original emission standards. University of Denver estimated from RSD measurements that more than a third of the current Sherman Way total emissions of CO and HC are contributed by less than 1% of the fleet and half of the total measured CO, HC, and NO was produced by 2.0%, 2.1%, and 5.0%, respectively, of the 13,000 measurements (Bishop et al, 2012). For these reasons, the potential differences in the contemporary inuse vehicle fleet that might be attributable to differences in the Federal and California programs are difficult to quantify.…”

“…Comparisons of RSD and model emission factors RSD measurements were included in the study to examine the distribution of emissions in the local fleet of light-duty vehicles (Bishop et al, 2012). As configured for this study, the RSD could not detect elevated exhaust plumes from trucks and buses.…”

“…We also compared the average of emission factors measured for about 13,000 vehicles by the University of Denver with a remote sensing device (RSD) with the average of the corresponding modeled emission factors. The RSD measurements were made on August 12-16, 2010, a week prior to the start of the Tunnel Study on eastbound Sherman Way about 600 m west of the Van Nuys tunnel (Bishop et al, 2012). Data from each of the three study participants were submitted in a blind manner to one of the study's coauthors (D. Lawson) at the National Renewable Energy Laboratory, so that they could be independently evaluated before they were shared among all study participants.…”

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

“…Mean NH 3 emissions at Peralta show no apparent instances of urea overdosing and are almost 2 orders of magnitude below the average NH 3 emissions of light-duty gasoline fleets. 35,36 A 2011 Mack tractor with an SCR system was measured at both locations. At the Port, this truck's gNO x /kg of fuel emissions and exhaust temperature were 31.2 g/kg and 120°C, and at Peralta they were 0.3 g/kg and 230°C (solid symbols in Figure 5).…”

Airborne measurements of the atmospheric emissions from a fuel ethanol refinery

“…Fuel ethanol is mostly used as E10 in gasoline vehicles. Fuel-based emission factors for NO x , SO 2 , and VOCs from gasoline vehicles that are averaged across a representative vehicle fleet are available from roadside and tunnel studies [Burgard et al, 2006;Bishop and Stedman, 2008;Bishop et al, 2012;McDonald et al, 2012;Gentner et al, 2013]. To estimate the vehicle emissions per liter of ethanol, we have to multiply the emissions from 10 L of E10 times the fraction of the emissions that is associated with ethanol only.…”