The Story of Ever Diminishing Vehicle Tailpipe Emissions as Observed in the Chicago, Illinois Area

Abstract

The University of Denver has collected on-road fuel specific vehicle emissions measurements in the Chicago area since 1989. This nearly 30 year record illustrates the large reductions in light-duty vehicle tailpipe emissions and the remarkable improvements in emissions control durability to maintain low emissions over increasing periods of time. Since 1989 fuel specific carbon monoxide (CO) emissions have been reduced by an order of magnitude and hydrocarbon (HC) emissions by more than a factor of 20. Nitric oxide (NO) emissions have only been collected since 1997 but have seen reductions of 79%. This has increased the skewness of the emissions distribution where the 2016 fleet’s 99th percentile contributes ∼3 times more of the 1990 total for CO and HC emissions. There are signs that these reductions may be leveling out as the emissions durability of Tier 2 vehicles in use today has almost eliminated the emissions reduction benefit of fleet turnover. Since 1997, the average age of the Chicago on-road fleet has increased 2 model years and the percentage of passenger vehicles has dropped from 71 to 52% of the fleet. Emissions are now so well controlled that the influence of driving mode has been completely eliminated as a factor for fuel specific CO and NO emissions.

Modeling Ozone in the Eastern U.S. using a Fuel-Based Mobile Source Emissions Inventory

“…The fraction of light trucks (e.g., vans, sport-utility vehicles, pick-up trucks) in the passenger vehicle fleet have grown with time. 65 In SI Figure S6, we breakdown NO x (panel a) and CO (panel b) emission factors between passenger cars and light trucks, and by Tier 0−2 emission standards. We also show how emission factors from remote sensing data compare with MOVES.…”

Three decades of on-road mobile source emissions reductions in South Los Angeles

“…Since the late 1980s light and medium-duty vehicle emissions have experienced significant reductions across the U.S. despite average fleet age increases due to the effects of the 2008 recession and improved vehicle longevity (Bishop and Haugen, 2018;Bishop and Stedman 2014). This is in part the result of improved emissions control technology driven by more stringent standards and dramatic increases in their useful life.…”

Statistical evaluation of on-road vehicle emissions measurement using a dual remote sensing technique

“…The above studies observed opposite NO emission trends due to the different fuel types concerned, i.e. gasoline and LPG vehicles in Bishop and Haugen (2018); Organ et al (2019) vs diesel vehicles in Huang et al (2018c); Pujadas et al (2017). RS studies showed that gasoline NOx reduced obviously in the past 15-20 years but diesel NOx did not reduce over the same period including those vehicles equipped with exhaust after-treatment systems for NOx control (Carslaw and Rhys-Tyler, 2013;Chen and Borken-Kleefeld, 2014).…”

“…The on-road RS technology is a rapid, non-intrusive and economical tool for the monitoring and control of in-use vehicle emissions, which has gained significant attention recently. Bishop and Haugen (2018) analysed a large RS dataset collected in Chicago during 1989 to 2016. Sharp reductions of emission factors (g/kg fuel) of light-duty vehicles were observed, with CO reduced by one order of magnitude since 1989, HC by a factor of >20 since 1989 and NO by 79% since 1997.…”