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Study shows new vehicles contribute to cleaner air

University of California, Riverside study shows new generation of gasoline vehicles contributes to cleaner air

(September 4, 2002)

Groundbreaking results of ongoing three-year study indicates that the vehicles produce extremely low emissions under real-world driving conditions

RIVERSIDE, Calif. - Emerging internal combustion engine technology can reduce emissions of harmful air pollutants to levels that were considered impossible only a few years ago, and this new generation of vehicle technology is contributing toward cleaner air, according to a University of California, Riverside study.

The university released the latest significant findings of its ongoing three-year Study of Extremely Low Emission Vehicles (SELEV) program during the first Clean Mobility Symposium, "Cars, Fuels and the Future of Air Quality," held on its campus today.

Initial results from the study indicate that, for the vehicles tested, the emissions of criteria pollutants (i.e., pollutants for which the U.S. Environmental Protection Agency has set national standards) are significantly below California average standards. The vehicles, certified to California's cleanest standards, are producing extremely low emissions under real-world driving conditions, resulting in improved air quality.

The university's Bourns College of Engineering - Center for Environmental Research and Technology (CE-CERT) established the SELEV program in partnership with industry and government agencies in June 2000 with the purpose of understanding, via direct measurements and modeling, the impact that new-generation vehicles with extremely low emissions have on overall air quality.

"This study is designed specifically to determine how engine technology can continue to decrease emissions while delivering the performance consumers expect from their cars," said Dr. Joseph Norbeck, director of CE-CERT. "The SELEV study is significant because most people will continue to drive internal combustion engine vehicles for many years."

CE-CERT has successfully developed the measurement technology to test emissions at lower levels. This technology is being used now to measure numerous Ultra Low Emission Vehicles (ULEVs) and Super Ultra Low Emission Vehicles (SULEVs). ULEV is a California standard that establishes stringent emission standards for non-methane organic gases (NMOG), oxides of nitrogen (NOx), and carbon monoxide (CO). SULEV is also a California standard, but with even tougher standards than ULEV. To be certified as Low Emission Vehicles (LEVs, ULEVs, or SULEVs), vehicles must meet stringent emission levels for NMOG, NOx, and CO on emissions certification tests.

"Ten years ago, nobody thought gasoline ULEVS and SULEVs would be possible," said Norbeck. "Now they're becoming common, and it's clear the emissions reductions they offer are significant." (See Table 1.)

Table 1: Comparison of California emission standards with sample of CE-CERT real-world measurements. CE-CERT measurements (in bold), which include cold-start, indicate the sample average for three different vehicles emissions categories. Units are in grams per mile.

State Std. (laboratory) CE-CERT (real world) State Std. (laboratory) CE-CERT (real world) State Std. (laboratory) CE-CERT (real world)
LEV 100,000 mi/10yrs 0.090 0.0608 4.20 0.8894 0.30 0.0545
ULEV 100,000 mi/10yrs 0.055 0.0096 2.10 0.0886 0.30 0.0267
SULEV1,2 120,000 mi/10yrs 0.010 0.01011,2 1.00 0.20071,2 0.02 0.01191,2

1 The original California Air Resources Board Low Emission Vehicle Program (LEV I) did not have a SULEV standard. The LEV II program, which includes a SULEV standard, becomes fully effective as of model year 2004. In addition to specifying SULEV standards, LEV II calls for reductions in NOx emissions from LEVs and ULEVs.
2 SULEV measurements made so far include several in extremely cold weather. Overall SULEV emissions are much lower than ULEV emissions under comparable conditions.

Non-methane organic gases are of concern because of their role in the formation of ozone, which has serious health effects. NOx, which is formed in the combustion chamber of the engine, is an irritant to the lungs and can aggravate respiratory problems. It is also a precursor to the production of ozone and very fine particulate matter in the atmosphere. CO, a colorless, odorless, and poisonous gas, results from incomplete combustion of fuel and is emitted directly from vehicle tailpipes. Its entry into the bloodstream through the lungs can hinder the blood's capacity to carry oxygen to organs and tissues.

The SELEV program is co-sponsored by the U.S. Environmental Protection Agency, the California Air Resources Board, Honda R&D Americas, Inc., ChevronTexaco North America Products, and the Manufacturers of Emission Controls Association. It encompasses both enhanced laboratory measurement approaches and new on-board measurement technologies and techniques.

Dr. James Lents, SELEV program manager, explained that SELEV's objectives include development of (1) emissions models that can represent how these vehicles perform in the real world, (2) air quality models to assess the impacts these vehicles will have on the environment, and (3) systems to integrate emissions models with air quality models. The SELEV team has already built a strong database of vehicle population and activity in Southern California.

Lents presented today data that suggest that the emissions are at extremely low levels in the lab and on the road. "Ultimately, we will use the experimental data in established modeling frameworks - or develop new modeling approaches - to consider broad-scale implications of environmental issues, technologies, and strategies," he said. "By integrating appropriate technical expertise from industry, government, and the academic community at every stage of the process, we assure that we are framing questions correctly, that we are obtaining appropriate data, and that we are processing the data in ways that minimize uncertainty."

Dr. Alan Lloyd, chairman of the California Air Resources Board, noted today that the goal is to have LEVs emitting less than 0.05 grams/mile each of hydrocarbons and NOx by the year 2010. "The LEV program has challenged manufacturers to develop advanced vehicle technologies, and manufacturers have gone a long way toward meeting the challenge" he said. "We're seeing progress toward even cleaner and more efficient technologies, and that is exciting. Fuel cells are fast becoming a reality and hybrid electric vehicles are already being sold today."

"Some of the newest gasoline-powered vehicles on the road today have made significant strides in addressing our clean air goals," said Ben Knight, vice president of Honda R&D Americas, Inc. "Engines designed to address cold-start emissions and that employ highly efficient catalysts are providing near-zero emission results in 'real-world' driving. This clean technology is being offered in the market today, and can help to bring us healthier air quality in the future. For example, our all-new 2003 Accords meet future CARB and EPA emission standards, and an Accord SULEV model sold in California is the first high-volume, near-zero-emissions vehicle to go on sale. Also, our 2002 CR-V is the cleanest gasoline-powered truck on sale in the United States," added Knight. "We value the research partnership with UC Riverside because we all have a stake in clean air, and CE-CERT's world-class work is giving us confidence we are heading down the right road."

In remarks developed for the symposium, Dave Reeves, president of ChevronTexaco North America Products, noted that society faces three critical issues surrounding autos and future propulsion technologies. "First, we need to consider the full economic, environmental and social consequences of alternative systems and fuels, and compare them with the remarkable performance of today's vehicles," he said. "Second, we need to let technologies compete freely, including conventional engines, gasoline-electric hybrids and hydrogen-powered fuel cell vehicles. And third, I believe we need to do a better job of recognizing what's already possible with new automobiles and industry trends. SELEV has clearly demonstrated that we're now seeing cars that help achieve cleaner air."

Slides presented at the symposium are available for viewing at

Joseph Norbeck, Ph.D., director Center for Environmental Research and Technology, addresses participants at UC Riverside Clean Mobility Symposium.
Joseph Norbeck, Ph.D., director Center for Environmental Research and Technology, addresses participants at UC Riverside Clean Mobility Symposium.

Dr. Alan Lloyd, chairman, California Air Resources Board, addresses participants at UC Riverside Clean Mobility Symposium
Dr. Alan Lloyd, chairman, California Air Resources Board, addresses participants at UC Riverside Clean Mobility Symposium

UC Riverside Clean Mobility Symposium participants tour testing labs
UC Riverside Clean Mobility Symposium participants tour testing labs

Media: Click on photo for print quality image.

Photo Credit: Bill Myerchin.

The University of California, Riverside offers undergraduate and graduate education to nearly 15,000 students and has a projected enrollment of 21,000 students by 2010. It is the fastest growing and most ethnically diverse campus of the preeminent ten-campus University of California system, the largest public research university system in the world. The picturesque 1,200-acre campus is located at the foot of the Box Springs Mountains near downtown Riverside in Southern California. More information about UC Riverside is available at or by calling 909-787-5185.

The University of California, Riverside ( is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.

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