On-road Heavy-duty Vehicle Emissions Monitoring System

Abstract

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.

Analysis of long‐term observations of NOx and CO in megacities and application to constraining emissions inventories

“…The steeper NO x /CO trend in our inventory between the mid‐1990s and mid‐2000s results from faster decline in LDGV CO emissions relative to NO x [ McDonald et al ., ] and the increasing importance of higher NO x ‐emitting heavy‐duty diesel vehicles (HDDVs) [ Bishop and Stedman , ; McDonald et al ., , ]. Decreasing NO x /CO after 2007 reflects the influence of the U.S. economic recession on freight traffic (which decreased NO x emissions), the beginning of the implementation of new HDDV NO x emission control technologies, e.g., by selective catalytic reduction (SCR) systems [ Bishop et al ., ], and initial implementation of Tier two emission standards on U.S. light‐duty vehicles where NO x controls were emphasized in the regulations [ Bishop and Stedman , ].…”

Summer ozone in the northern Front Range metropolitan area: weekend–weekday effects, temperature dependences, and the impact of drought

“…The decreasing NO * 2 at the CAMP site appears to be converging with the NO * 2 at the Welby site. It is unlikely that traffic patterns are assimilating between the two sites, and a more plausible explanation is that emission control technologies on heavy-duty commercial fleet vehicles are reducing the impact on emissions of those specific vehicles and reducing the measurable NO * 2 (Bishop et al, 2015). The O 3 decreased across the NFRMA outside of the most highly trafficked regions in Denver, again consistent with the hypothesis that the NFRMA P (O 3 ) regime has transitioned from NO x -saturated chemistry towards peak P (O 3 ).…”

The Advanced Collaborative Emissions Study (ACES) of 2007- and 2010-Emissions Compliant Heavy-Duty Diesel Engines: Characterization of Emissions and Health Effects

“…Studies that have examined emissions under present realworld conditions from individual vehicles have reported reductions in PM and NOx emissions as the proportion of new or retrofitted diesel engines increases, showing the effectiveness of in-use DPFs as well as of SCR [3,4,21]. However, it should be noted that the test conditions, by necessity of short duration, did not address the durability of the emission controls over the life of the engines.…”

“…As with the introduction of any new technology on a large scale in the marketplace, some challenges with the use of the new aftertreatment technologies have been observed. First, although DPFs are very effective, some recent reports suggest that, under real-world conditions, a small proportion of newtechnology engines still produce higher emissions of PM [4,7]. Starting with 2016 model year, HHDDE vehicles are equipped with onboard diagnostics (OBD) and with PM and NO X sensors to help monitor the effectiveness of the aftertreatment system, and these trigger a malfunction indicator light when the emissions exceed regulatory OBD threshold.…”

“…Regulated pollutants were sampled from the CVS. CO (and CO 2 ) were measured using nondispersive infrared detectors, NOx was measured using a heated chemiluminescence detector, and total hydrocarbons (THCs) and CH 4 were measured with heated flame-ionization detectors. PM mass was measured gravimetrically on PM collected on a 47-mm Teflon filter.…”