DENVER - Roadside vehicle emissions testing, created in Colorado and pioneered in Northern Colorado more than a decade ago, is returning to portions of Larimer and Weld counties, according to the Colorado Department of Public Health and Environment.

Beginning June 1, roadside emissions testing units, called RapidScreen, will begin rotating among 22 pre-approved locations throughout the expanded vehicle emissions testing area in Larimer and Weld counties. Data will be collected once the overall program expansion is fully implemented Nov. 1.

RapidScreen units identify eligible "clean" vehicles. RapidScreen equipment analyzes the exhaust from a vehicle as it passes by on the road. It uses infrared and ultraviolet light to measure the concentration of specific pollutants in the exhaust plume. A computer records vehicle speed and acceleration, and a photo of the license plate is taken so eligible vehicles can be matched to registration records.

To qualify, vehicles must be well-maintained and license plates must be clean and unobstructed. If roadside sensors confirm eligibility, vehicle owners will be notified on their vehicle registration renewal cards that they can complete the entire registration process without having to make a trip to a vehicle emissions testing station.

Eligible vehicles include most light-duty, 1982-and-newer gasoline-powered cars and trucks.

State officials believe RapidScreen units will collect between 2,000 and 3,000 valid readings per site per day. Initial goals are to identify as much as 20 percent of the eligible vehicle fleet in Larimer and Weld counties, meaning one in five vehicles may not have to visit an Air Care Colorado testing station.

More information is available at the Air Care Colorado Web site at