Maddison Automotive provides emission testing for Wales, and all of Waukesha County. No appointment is necessary.
Feel free to review the following information about emission testing from the Wisconsin DMV website.

When are emission tests required?

Before registration renewal. Vehicles require an emission test every other year before license plate renewal, beginning in the third year following the vehicle’s model year. (For example, model year 2008 vehicles first require a test in 2011.) Renewal notices will indicate if a test is due.

The vehicle must pass the emission test before registration renewal. Failure to pass the test prevents issuance of the annual plate sticker, which makes the vehicle illegal to operate after the registration (plate) expires. If you mailed your renewal without the passing the emission test, take your vehicle to one of the test stations. DMV will automatically receive the successful test information and issue the registration and sticker. Your registration and stickers should arrive within a week to 10 days.

A test is not required if the vehicle passed a test within 180 days of the registration expiration date. You can check whether your vehicle is due for a test within the next 180 days by entering your license plate on WisDOT’s plate inquiry page. If the inquiry result page includes the statement “IM test is needed,” your vehicle is due for a test (“IM” = Inspection Maintenance). You do not need a renewal notice or letter from WisDOT in order to have your vehicle tested.

Why vehicles are tested

The federal Clean Air Act mandates the operation of vehicle emission inspection and maintenance programs in areas throughout the nation with significant air quality issues, including Southeastern Wisconsin. In addition to identifying vehicles violating state emission standards, the Wisconsin Vehicle Inspection Program (WVIP) also identifies vehicles with tampered emission control equipment. The owners of these vehicles are required to have tampered items repaired, replaced, or otherwise returned to proper working order.

Motor vehicles are a major source of air pollutants in metropolitan areas. Vehicle exhaust contains carbon monoxide and other pollutants – volatile organic compounds and nitrogen oxides – that react to form ground level ozone. Motor vehicles emit about one-third of Southeastern Wisconsin’s volatile organic compounds (mostly hydrocarbons) and about 60% of its carbon monoxide.

Program information

The Department of Natural Resources (DNR) sets vehicle emission standards for the WVIP, and WisDOT administers the program. Currently, WisDOT contracts with Systech International to conduct vehicle emission tests. WisDOT audits inspection equipment and procedures at each inspection location to assure accurate results.

Required inspections are free to the motorist, as are the first two re-inspections (if needed). Subsequent inspections, as well as voluntary inspections, cost $15 each.

The WVIP conducts approximately 650,000 inspections each year.