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Since 1984, Salt Lake County has had a motor vehicle emission inspection and maintenance (I/M) program to control and reduce air pollution. Motorists take their vehicles to authorized test stations for annual tests to insure that their vehicles are working properly and not polluting the air. Although the program has been a success, air pollution in the area is projected to increase. The number of vehicles traveling on Salt Lake County roads has increased dramatically over the past few years. The trend continues and with more vehicles on the roadways, we will see an increase in air pollution.

Over the past 20 years urban sprawl, working habits, and commuting patterns have caused a dramatic increase in the number of vehicle miles traveled.   Motorists who once drove  12,000 - 15,000 miles per year are now driving 15,000 - 20,000 miles annually. This increase in vehicle miles traveled (VMT) means more pollutants will be emitted into the atmosphere every year.

There are several technological and regulatory reasons for upgrading the vehicle emissions testing program.

Changing vehicle technology has required implementation of upgraded vehicle testing procedures. Modern vehicles must be tested on more sophisticated equipment to accurately determine which are truly gross polluters. Changes in federal clean air standards and state regulations require Salt Lake County to upgrade the emissions testing effort in order to meet State Implementation Plans and federal mandates.

New testing and diagnostic technologies have been developed for the aftermarket industry that far exceed the capabilities of older systems. These technologies assist technicians to detect more pollutants and to more accurately diagnose and repair vehicle emissions failures.

Geography and weather conditions in the valley continue to exacerbate pollution problems. Winter temperature inversions trap pollutants and cause unhealthy and unsightly conditions. While we cannot affect temperature inversions, we can make every effort to reduce pollutants emitted into the air.

Model year vehicles 1995 and older are tested using a dynamometer or “treadmill for vehicles.” Vehicles newer than 1995 model years are tested using the onboard diagnostics system (OBD) manufactured in those vehicles. The OBD system uses the vehicle’s onboard computer to run self-diagnostics on the emission control components. Diesel powered vehicles are tested for excessive emissions based on the darkness or opacity of the exhaust. There are approximately 340 privately owned testing facilities in Salt Lake County. Click on the “Station Locations (I/M)” link for a list of testing facilities.

The enhanced emissions inspection program for Salt Lake County provides improved testing for pollutants, better service for motorists, and additional help for mechanics and technicians to repair failed vehicles. The result is cleaner air and improved services for Salt Lake County residents.