What's New I Testing Requirements I Testing Elements I FAQ

Background

Vehicle emission testing originally started in southeastern Wisconsin in 1984. This highly-effective program has prevented 40,000 tons of carbon monoxide and ozone-forming hydrocarbons from entering the air each year. It is an important reason why the federal air quality standard for carbon monoxide--which was exceeded 35 times between 1977 to 1984--was not exceeded even once in southeastern Wisconsin after 1984. The Wisconsin Vehicle Inspection Program (WIVIP) contributes about one-fourth of the emission reductions in Wisconsin's federally-required plan for achieving 24% reductions of volatile organic compounds (hydrocarbons) in the Milwaukee area. Fixing cars is also one of the most cost-effective ways to clean the air. The U.S. Environmental Protection Agency estimates that vehicle inspection programs, such as the WIVIP, are at least 10 times more cost-effective than new controls on small and large industrial sources. The fuel saving realized by effective repairs has helped offset the cost of the repairs.

Testing Procedures Keep Pace With New Vehicle Technology

As vehicle technology has changed over the years, so has the testing procedures used by the Wisconsin Vehicle Inspection Program (WIVIP). When the WIVIP began in 1984, vehicles were tested at idle only. While the program's "idle test" was very effective for testing the carbureted pre- 1981 model year vehicles, a more comprehensive test was needed to test newer vehicles with advanced computer-controlled emission control systems. Furthermore, the original program did not test for emissions of evaporative hydrocarbons--vapors that escape from various points of the vehicle's fuel system. On a hot summer day these vapors account for about 40% of the total motor vehicle hydrocarbon emissions in southeastern Wisconsin. These deficiencies prevented Wisconsin's original inspection program from realizing its full potential for improving air quality. Enhanced I/M was the next logical step.

The transition to enhanced I/M that occurred in December 1995 was an evolutionary rather than a revolutionary change. The basic program requirements did not change: Vehicles still are required to periodically undergo tests for excess emissions at high-volume test facilities. Vehicles failing a test still need to be repaired and retested. The counties subject to the program did not change. The major enhancement involved new test procedures that more effectively identify high-emitting vehicles. Improving repairs and public convenience were also major focuses of the enhancement effort.

Next Step

Beginning July 1, 2008, only model year 1996 and newer vehicles weighing up to 8,500 lb. GVWR will require an On-Board Diagnostic inspection.  These are OBDII-compliant vehicles – vehicles equipped with a second-generation on-board diagnostic computer system.  Older and heavier vehicles are not OBDII-compliant and are being exempted from the I/M requirement.