Emissions Tested While You Drive

04/03/96

Donald Stedman invented a device that can test your emissions as you drive down the road. His emissions tester shoots a beam of infrared light across passing traffic and measures how much light makes it across the road after a car passes. The device analyzes the carbon monoxide and hydrocarbon content of each passing car's exhaust in about a second.

Stedman's idea is to market the device as a way of filtering clean cars out of states' emissions testing processes by giving them a passing grade as they zip off down the road. He says that screening clean cars out of the process with his remote sensing devices could upgrade and cheapen annual emissions testing.

As clean cars pass the devices, a digital video camera will snap a shot of the car's license plate. The state can then send a clean bill of health to that car, obviating the need for more testing for the year.

The EPA is not ready to give up all emissions testing in favor of the remote sensing devices, as they are not wholly reliable. Nonetheless, Craig Rendahl, an air management specialist with the Wisconsin Department of Natural Resources says that the tests are becoming increasingly accurate. He sites a study of the sensors that shows that only 3% of the cars that failed a remote emissions test did so erroneously, and that all of the cars that failed erroneously were made before 1992. Stedman claims that an independently conducted study found his remote sensing devices to be 95 percent accurate.

Some states (California, Connecticut, Maryland, Wisconsin, and New Mexico) are already using the devices and have replaced random emissions testing with notices sent out in the mail after a vehicle fails the remote test. Other states want to use the test to screen clean cars out of the testing process, but that would require EPA approval.

Paul Dever -- The Auto Channel