Environmental Impacts of High-Emitting Vehicles

Abstract

High-emitting vehicles (HEVs), also known as high emitters, are responsible for a large proportion of total mobile-source emissions, even though they represent a small portion of the total vehicle fleet. Studies conducted in the 1990s indicated that between 7% and 12% of the vehicle fleet accounted for 41% to 63% of total carbon monoxide (CO) emissions; 10% of vehicles were responsible for 47% to 65% of hydrocarbon (HC) emissions; and 10% of vehicles were responsible for 32% of nitrogen oxide (NOx) emissions. However, these conclusions were confined both temporally and spatially because the studies used remote-sensing data or inspection and maintenance test data that were collected at a specific location and time. Consequently, the objective of this study is to quantify the contribution of HEVs at a network level by using comprehensive modal emission models (CMEMs) and Virginia Tech-Micro (VT-Micro) microscopic vehicle emission models. This study applies two approaches besides the use of the CMEM and VT-Micro models. First, the study quantifies the HEVs’ contribution by using different predefined drive cycles. Second, a simulation of a highway and arterial network is applied. The study results demonstrate that HEV emission contributions to total HC and CO emissions are consistent with what is reported in the literature. However, the contribution of NOx emissions is greater than what is reported in the literature. The study demonstrates that the contribution of HEVs to total vehicle emissions is dependent on the type of roadway facility (arterials versus highways), the background normal vehicle composition, and the composition of HEVs.

Design Criteria for Future Fuels and Related Power Systems Addressing the Impacts of Non-CO2 Pollutants on Human Health and Climate Change

“…A critical issue in the development of power-generating systems, specifically directed at power systems used in mobile sources, is the improvement and acceptance of on-board diagnostic systems to identify high-emissions vehicles, which can lead to corrective action. As previously stated, a small percentage of improperly operating vehicles are often large contributors to non-CO 2 emissions (70)(71)(72)(73). Under these circumstances, the design of low-emissions fuels should be directed at these poorly operating vehicles with high emissions, which are differentially impacted by fuel www.annualreviews.org • Fuel Design to Reduce Adverse Impacts 5.13 Changes may still occur before final publication online and in print composition (74).…”

“…Several studies in the United States and other parts of the world have shown that 5% to 10% of the vehicles operating on roadways can make up 30% to 75% of the exhaust emissions (70)(71)(72)(73). These high-emissions vehicles include vehicles with improperly working power systems or improperly working emissions control devices and very old or off-market vehicles that were not built to meet contemporary emissions standards.…”