Vehicle Emissions Reduction

Summarized below are some of the more recent experiences in different parts of the world with vehicle inspection and maintenance efforts.

In a recent demonstration of centralized IM capability, in 1992, the province of British Columbia implemented an emissions inspection and maintenance (IM) program in the Lower Fraser Valley (LFV) area, which incorporated then state of the art inspection procedures. It was the first IM program to measure hydrocarbons (HC), carbon monoxide (CO) and the oxides of nitrogen (NOX) using the acceleration simulation mode (ASM) test, which is a loaded mode test simulating vehicle acceleration. The inspection also included an idle test and an anti tampering check to further assure that high emitting vehicles were identified and repaired.

Before and after repair

               HC(g/km)           CO             NOx
Model year   before after    before after    before after
pre-81       3.5    1.9      33     17       3.3    1.4 
81-87        2.2    1.2      29     12       2.8    2.1 
post-87      0.49   0.24     8.6    2.9      3.0    1.7 

The above Table summarizes the emissions reductions following repairs for HC, CO and NOx for each of the model year groups and illustrates that repairs significantly reduced HC, CO and NOx of the failed vehicles in all model year groups. Overall, about 88% of the repairs were effective in reducing emissions.

Based on the audit results, overall emissions were reduced by approximately 20% for HC, 24% for CO and 2.7% for NOX.

In addition to the emissions reductions, the audit program found that fuel economy for the failed vehicles improved by approximately 5.5% for an estimated annual savings of $72 per year per vehicle.

The audit program also demonstrated that the centralized program was resulting in a very high quality test program. For example, after reviewing over 2 million tests, the auditor concluded that in only 1.1% were incorrect emissions standards applied.

Not one instance was found where a vehicle was given a conditional pass or waiver inappropriately. About 1% of the failed vehicles were found to be receiving waivers even though their emissions are excessive, i.e., they exceed either 10% CO, 2,000 ppm HC or 4,000 ppm NOx. If the cost limits were increased such that this percentage were halved, the auditor concluded that HC and CO reductions from the program would each increase by about 5%.

Available data also indicates that many vehicles are repaired sufficiently that they remain low emitting. For example, almost 53,000 vehicles that failed the test the first year were repaired well enough to pass the following year.

Overall these data confirm that IM programs when properly performed in a centralized facility using a loaded mode test can and do achieve a substantial reduction in emissions. These reductions are accompanied by substantial fuel savings. According to the auditor, improvements to the program such as including evaporative testing, reducing or eliminating cost waivers, adding the IM240 test or tightening the standards could all increase the overall benefits significantly.

Up until the end of 1995 a dual IM system had been in effect in Mexico City combining both centralized (test only) facilities and decentralized private garages (combined test and repair).

Over time, it became increasingly clear that the private garage system was not working. As one measure, for example, the failure rate in the private garages averaged about 9 percent whereas in the centralized lanes, the failure rate was about 16 percent.

Stations conducting improper or fraudulent inspections were taken to court on several occasions with the courts usually agreeing to shut them down. By the end of 1995, as part of the development of the "Programma para Mejotrar la Calidad del Aire en el Valle de Mexico, 1995-2000" (the New Program), and in recognition of the critical role that IM had and would play in the Mexico City strategy, the Federal District (DDF) decided to close all the private garage inspection stations and to switch to a completely centralized system. This politically difficult decision reflected a conclusion that it would be virtually impossible to police the private garage system on a case-by-case basis.

Since 1981 Colorado has operated an IM program in the metropolitan areas along the Front Range of the Rocky Mountains. Until 1995 Automobile Inspection and Repair (AIR) program consisted of approximately one thousand independently operated facilities, performing a variety of idle-tests procedures and analyzer technologies. In 1995 Colorado's AIR program was upgraded to meet USEPA requirements by implementing an enhanced IM program in the six-county Denver metropolitan area.

The enhanced IM program is a bifurcated network of centralized and independently run decentralized test-only facilities. Decentralized facilities are authorized to test 1981 and older model year vehicles employing a two-speed idle test. Centralized contractor-operated facilities test both 1981 and older vehicles using the two-speed idle test procedure, and 1982 and newer model-year vehicles using the IM240 loaded-mode transient mass emissions test. There are 15 centralized facilities operating 72 lanes and about sixty independent facilities in the enhanced program area, conducting about one million tests per year.

The primary focus of the Colorado IM program is to reduce carbon monoxide (CO) emissions. All vehicles are tested for CO and hydrocarbons emissions, while only newer vehicles subject to IM240 testing are also tested for NOx emissions levels. With phase-in cut points in place, the enhanced program is responsible for reducing CO emissions 30-34%.

As the enhanced program affects more vehicles and cut points are made increasingly more stringent, the emissions reduction benefit of the enhanced program will significantly increase.

Colorado's 1997 IM240 failure rate was 7 percent with an average per vehicle CO emission benefit per repair of 66 percent. The average cost of repairs for vehicles failing the IM240 was $189 (US). Repair costs are partially offset by an average 7 percent increase in fuel economy due to repair.

The administration of the Colorado IM program is divided among several state agencies. The Department of Public Health and Environment is responsible for the technical aspects of the program and is required to report to the Air Quality Control Commission. The Air Quality Control Commission is ensures the IM program complies with state and federal laws. The Department of Revenue is responsible for licensing facilities, inspectors and mechanics, and all enforcement aspects of the program including auditing functions.