Colorado Diesel Inspection and Maintenance Programs

The State of Colorado controls heavy-duty diesel vehicle emissions through two diesel inspection and maintenance (I/M) programs. The first diesel I/M program is the Diesel Opacity Inspection Program (DOIP) for fleets smaller than nine vehicles. The second, the Diesel Fleet Self Certification Program (DFSCP), is for fleets of nine or more heavy-duty vehicles. In addition to these two programs, specially trained police officers operate a Roadside Enforcement Program across Colorado.

Colorado’s diesel I/M programs measure the opacity (density) of the diesel’s smoke emissions. This opacity rating is a percentage measuring the blockage of light transmission by smoke and particles

The two I/M programs outlined below include revisions that passed through the legislative session this year as part of HB03-1053. The changes will take effect near the end of 2003.

Diesel Opacity Inspection Program (DOIP) for Small Fleets

Smaller diesel fleets registered or operating from the Automobile Inspection and Readjustment (AIR) Program area* take part in the DOIP. This program is for fleets of less than nine heavy-duty diesel vehicles (over 14,000 lbs. GVWR), not subject to the large fleet self-certification program described below. The DOIP requires that eligible vehicles be inspected through a full-load lugdown test on a dynamometer with an opacity meter on a biennial basis by private, state-licensed diesel inspection stations. The opacity cut point under the DOIP is 35 percent for naturally-aspirated vehicles and 20 percent for turbo-charged vehicles for five seconds.

In calendar year 2002, over 14,000 heavy-duty vehicles were tested with an average test costing $74. Overall, there was a 2 percent failure rate. The average cost of repairs to vehicles failing their test was approximately $465.

*The AIR Program area includes all or part of 10 Front Range Counties along the I-25 Corridor from Colorado Springs through the Denver-Boulder area, north through Fort Collins and Greeley.

Repairs

Vehicles that smoke excessively and do not pass the DOIP must be repaired to bring them into compliance with the state opacity standard. Some vehicles will not meet the opacity standard even after extensive repairs and may apply for a one-year waiver. A minimum expenditure of $1,500 for heavy-duty diesels must be spent attempting to repair the vehicle to be eligible to apply for a waiver.

Diesel Fleet Self Certification Program (DFSCP) for Large Fleets

Fleets subject to the DFSCP are those within the AIR Program area* with nine or more diesel vehicles of more than 14,000 pounds GVWR. The program requires fleet owners and operators to self inspect and certify their vehicles annually to maintain compliance with state smoke opacity standards. A full-load test is required, but lugdown, stall, or snap acceleration test options are allowed, and the test can be done on-road or with a dynamometer. Additionally, this certification can be done either through the use of an opacity meter or a fleet employee who is a “certified observer” (for vehicles less than 10 years old). This observer must attend certification courses and register with the Colorado Department of Public Health and Environment. Additionally, fleets are required to adhere to an engine-related preventative maintenance schedule.

The lugdown opacity cut point under the DFSCP is also 35 percent for naturally-aspirated vehicles and 20 percent for turbo-charged vehicles for five seconds. The snap acceleration opacity cutpoints are 55 percent for 1991 and older and 40 percent for 1992 and newer diesels. In calendar year 2002, over 15,000 vehicles were tested and 0.64 percent failed the test.

Proof of passing the opacity test is necessary as a prerequisite to registration. It is also required of those vehicles operating in the AIR Program area with out-of-state license plates.

*The AIR Program area includes all or part of 10 Front Range Counties along the I-25 Corridor from Colorado Springs through the Denver-Boulder area, north through Fort Collins and Greeley.

Repairs

Heavy-duty diesel vehicles in the DFSCP must comply with the state’s opacity standards. There is no waiver offered under this program. Fleet owners must either fix or retire the vehicle.

For more information, contact Doug Decker with the Colorado Department of Public Health and Environment at (303) 692-3126.

Sources

Colorado Department of Public Health and Environment
Report to the Regional Air Quality Council and the Air Quality Control Commission – Reducing Diesel Emissions in the Denver Region, May 2002