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Vehicle emission testing

Where tests are required | When tests are required | Testing stations | Procedure

Motor vehicles are a major source of air pollutants in metropolitan areas. Vehicle exhaust emissions include carbon monoxide and volatile organic compounds (VOCs). In Southeastern Wisconsin, motor vehicles emit about one-third of volatile organic compounds (mostly hydrocarbons) and 60% of carbon monoxide present.

The federal Clean Air Act spells out air quality standards that all areas of the United States must meet. Southeastern Wisconsin is one of over 90 metropolitan areas in 35 states violating these standards. The Clean Air Act mandates the operation of state-administered vehicle emission inspection and maintenance programs in many of these areas, including Southeastern Wisconsin. 

The purpose of the Wisconsin Vehicle Inspection Program (VIP) is to identify vehicles:

• With excessive exhaust emissions and require them to meet reasonable emission standards to reduce vehicle-related air pollution
• That have experienced emission equipment tampering, regardless of how caused. The owners of these vehicles are required to have "tampered" items repaired, replaced, or adjusted to proper working order before the vehicle can be registered.

Where tests are required

Emission tests are required on automobiles and on trucks with a manufacturer's gross vehicle weight less than 10,000 pounds that are customarily kept in the Wisconsin counties of:

• Kenosha
• Milwaukee
• Ozaukee
• Racine
• Sheboygan
• Washington
• Waukesha

Exceptions are vehicles produced prior to the 1968 model year, diesel-powered vehicles and motorcycles. Approximately 900,000 tests are conducted each year.

WisDOT contracts with Envirotest Systems Corporation to conduct vehicle emission inspections, or tests. WisDOT audits test equipment at each vehicle emission test station weekly to assure accurate testing. The required test is free.

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When tests are required

Vehicles are tested every second year at the time of renewal of license plates, beginning in the third year following the vehicle’s model year. Renewal notices indicate if testing is required. In addition, vehicles more than 5 model years old require testing within 45 days following registration by a new owner. WisDOT mails a letter to the new owner outlining the testing requirements.

When a vehicle is not tested by the license plate renewal deadline, the vehicle registration is suspended. In such cases, the owner must satisfy emissions testing to continue to legally operate their vehicle.

Testing stations

Vehicles can be tested at any of the 12 vehicle inspection facilities (external link) located in Sheboygan and throughout southeastern Wisconsin.

Procedure

When motorists enter the test facility, they hand the inspector the license plate renewal notice. The inspector enters essential information into a computer that automatically selects the proper test-type and standards for the vehicle's weight and model year. Most model year 1996 and newer vehicles equipped with On Board Diagnostic II (OBDII) computer systems are tested by means of a computer "health-check". This check consists of plugging into the vehicle's computer and downloading emission system information.  On other vehicles the tailpipe emissions are measured while the vehicle is driven on a treadmill-like device called a dynamometer. The vehicle is operated over a driving cycle that simulates typical city driving and includes periods of acceleration, cruise and deceleration. After the OBD check or emission test, the vehicle's gas cap is tested to ensure that it seals properly.

After all of the tests are complete, motorists receive results on a computer generated report form. This report contains the results of the OBD inspection or emissions test and the gas cap inspection. When vehicles pass both portions of the vehicle inspection the registration can be renewed while at the test site, or the owner can renew by mail or the Internet, or in person at any of the WisDOT DMV service centers offering vehicle registration service. All of the test facilities have the ability to process the renewals. The computer matches records from the inspection stations with WisDOT's registration records to verify that the inspection has taken place.

If a vehicle fails any portion of the test, the owner must have repairs performed and/or replace the gas cap prior to being retested. Satisfactory completion of the test requirements is necessary before the license plate can be renewed. The inspector gives all motorists an informational brochure at the time of the initial test to explain the repair and retest process.

Call (414) 266-1080 or (800) 242-7510 for more information.

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All external hyperlinks are provided for your information and for the benefit of the general public. The Wisconsin Department of Transportation does not testify to, sponsor or endorse the accuracy of the information provided on externally linked pages.

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Questions about the content of this page:
Bureau of Vehicle Services, bur-veh-services.dmv@dot.state.wi.us
Last modified: April 9, 2007