Program Overview | Program Rationale | An Environmental Success Story | Background | Emissions Testing Requirements

Program Overview

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Program Rationale

The Wisconsin Vehicle Inspection Program plays a key role in the reduction of harmful pollutants

Southeastern Wisconsin is one of more than 120 metropolitan areas with ground-level ozone levels that exceed federal air quality standards.  Excessive air pollution is a public health hazard.  Geographically, as part of the south Lake Michigan air basin, southeastern Wisconsin is one of the worst areas in the country for ozone pollution.

Ground-Level Ozone Facts

Ground level ozone is:

• not emitted directly into the air;
• caused by a chemical reaction between volatile organic compounds (VOCs) – mostly hydrocarbons – and nitrogen oxides (NOx) in the presence of sunlight;
• exacerbated by the presence of carbon monoxide (CO);
• worst in summer;
• a result largely of motor vehicles.  They emit over one-third of all ozone-forming pollutants.

While ozone in the upper atmosphere protects the earth from harmful ultraviolet radiation, high concentrations at ground level can be harmful to human health and the environment.  Specifically, ground level ozone:

• decreases lung capacity and other functions.
• inflames airway passages.
• reduces the effectiveness of the respiratory immune system.
• damages crops and forests.

Studies show that prevailing winds can transport air pollution from one area to another. The four states that border Lake Michigan are working cooperatively to find solutions that improve regional air quality. Operating vehicle inspection and maintenance programs in urbanized counties is an important part of this effort.

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The Wisconsin Vehicle Inspection Program (WVIP) is an integral part of the state’s overall strategy to improve air quality in southeastern Wisconsin - one of over 120 metropolitan areas in 31 states (plus the District of Columbia) with ozone pollution levels exceeding federal health standards.  Motor vehicles produce approximately one third of southeast Wisconsin’s VOC and NOx emissions that contribute to the formation of ozone, and more than half of its carbon monoxide emissions.  High ground-level ozone concentrations contribute to upper respiratory problems and can damage crops and forests.  Through biennial testing the WVIP identifies vehicles that exceed exhaust and evaporative emission standards and prevents registration of those vehicles until they comply.

The WVIP works, preventing more than 40,000 tons of carbon monoxide and about 5,000 tons of ozone-forming hydrocarbons and NOx from entering the air each year.  It is an important reason why Wisconsin has not exceeded the federal carbon monoxide air quality standard once since 1984 – when testing began – but exceeded it 35 times between 1977 and 1984.

Ground-level ozone formation is of particular concern in warm weather.  The WVIP achieved the following (estimated) reductions in ozone-forming emission on a typically hot summer day in 2006:

• 5.2 tons of VOC emissions (an 12.0% reduction in motor vehicle emissions)
• 6.9 tons of NOx (7.3% reduction)
• 80.7 tons of CO (14.8% reduction)

This all adds up to cleaner, healthier air for Wisconsinites.

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Background

The Wisconsin Department of Transportation (WisDOT) implemented the Wisconsin Vehicle Inspection Program (WVIP) in April 1984, in response to the federal Clean Air Act requirements.  A major focus of the Clean Air Act is to reduce emissions that form ground-level ozone.   Motor vehicles, industries, and smaller area sources such as lawn mowers, power boats, paints, solvents and other consumer products emit these ozone precursors.  Areas exceeding federal air quality standards –established under the Clean Air Act are designated as non-attainment and are required by federal law to reduce emissions.

The WVIP is one of the primary components of the strategy to reduce air pollution in southeastern Wisconsin area.  Each year, over 600,000 cars and light duty trucks in a seven county region of southeastern Wisconsin’s ozone non-attainment area are tested for emissions.  The program covers more than 2,500 square miles over seven counties: Kenosha, Milwaukee, Ozaukee, Racine, Sheboygan, Washington, and Waukesha.  Vehicles are tested in 12 stations located in Burlington, Cedarburg, Kenosha, Milwaukee, Racine, Sheboygan, Waukesha, West Bend, and West Allis.

The emissions tests are free to the motorist, but cost WisDOT about $15 each.  The state Transportation and Petroleum Environmental Cleanup Fund Act (PECFA) funds pay for the program.

Emissions testing is conducted by Envirotest Wisconsin Inc., which has operated the program under contract to WisDOT since it began.  WisDOT administers the program, while the Wisconsin Department of Natural Resources (DNR) establishes the applicable vehicle emissions limitations in accordance with federal guidance.

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Emissions Testing Requirements

The WVIP currently requires testing of all gasoline or alternative-fueled vehicles that are model year (MY) 1968 and newer and weigh 10,000 pounds gross vehicle weight rating (GVWR) or less.  In general, vehicles are tested biennially (every other year).  A vehicle receives its first test in the third calendar year after its model year and every two years thereafter (e.g., MY 2000 vehicles are tested in 2003, 2005, etc.).  Collector vehicles are tested only at initial license plate registration and at change of ownership.  Vehicles older than MY 1968, vehicles over 10,000 pounds GVWR, diesel-fueled vehicles, motorcycles, and electric vehicles are exempt from testing.

Vehicles are tested for hydrocarbon, nitrogen oxide and carbon monoxide tailpipe emissions.  In addition, most vehicles are given a gas-cap pressure test to ensure that the gas cap is sealing properly. Satisfactory completion of the emissions test (tailpipe or OBDII test, plus gas cap test) is required for license plate renewal.  In addition, vehicles at least five model years old must meet the emissions testing requirements within 45 days of changing ownership.

Vehicles normally receive one of two tests, depending on their model year (MY) and weight.  MY 1996 and newer vehicles up to 8,500 lb. receive an on-board diagnostic (OBD II) test, in which the vehicle’s on-board computer is scanned for emission-related problems.  The test does not change or affect the vehicle’s computer in any way.  If the vehicle’s MIL light (check-engine light) has been commanded on due to an emission equipment problem, then the vehicle fails the inspection.  Most vehicles that fail an initial OBDII inspection are successfully repaired prior to retest.

Vehicles that are model year 1968 through 1995, and 1996 and newer vehicles over 8,500 lb., receive an IM240 test, in which the vehicle’s tailpipe emissions are measured while the vehicle is “driven” through a 240-second drive cycle on a treadmill-like device called a dynamometer.  The IM240 test is a transient emission test, which measures tailpipe emissions under varying engine load conditions.  In instances where neither the OBDII test nor the IM240 test can be properly or safely administered, a vehicle may receive an idle test.  As its name suggests, the idle test measures tailpipe emissions while the vehicle idles.

For both the IM240 and idle tests, a vehicle’s tailpipe emissions are compared to a set of model year-specific allowable emission limits.  A vehicle that exceeds these limits, or cutpoints, fails the emissions test.  The DNR establishes the cutpoints necessary to comply with federal air quality standards.  Their cutpoints produce an approximate 20% failure rate for vehicle model years 1981 and older. The cutpoints are set at more than double the pollution levels that vehicles should emit if properly tuned and maintained.  This helps ensure that a relatively well-maintained vehicle will pass the emission test.

Gas caps from MY 1971 and newer vehicles are tested for integrity, because poor seals allow hydrocarbon vapors to escape from the gas tank.  Gas caps are tested by removing from the vehicle and attaching to a pressure test rig.  Failure of the gas cap pressure test requires motorists to replace the gas cap and pass a retest.

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