California Air Resources Board

SACRAMENTO - In a move to reduce one of the state's most visible pollution problems and biggest sources of public complaints, the Air Resources Board (ARB) has adopted a Smog Check style roadside inspection for diesel "big-rig" trucks, buses and other heavy vehicles.

The anti-soot test is not limited to vehicles registered in California, but includes all that are driven in the state, regardless of where in the country they are registered.

In addition to random roadside tests administered by nine roving teams of ARB and California Highway Patrol employees, testing is also required for buses and trucks that are maintained in fleet garages. The ARB/CHP teams are expected to test about 38,000 trucks a year.

While the main focus of the testing is the 250,000 diesel trucks and buses that are driven in California, another 200,000 gasoline-powered vehicles, from motor homes to delivery trucks, would be inspected to prevent tampering with anti-smog systems.

The California program is not the first in the nation since five other states also test diesel trucks. The ARB test, however, is expected to be the most effective because of the precise testing equipment it will use and the strict enforcement of its pass/fail standards.

The new test is similar to Smog Check, the inspection of pollution controls on gasoline-powered passenger cars conducted once every two years. Like Smog Check, the proposed diesel tests would target the dirtiest one-third of the trucks and buses that produce up to 70 percent of the 85 tons per day of soot-like particulate emitted in California.

The testing, which will begin in the Spring of 1991, is expected to reduce overall emissions from the entire fleet by 17 percent, while emissions from individual trucks will be cut as much as two-thirds.

Under the test, emissions will be measured by their density while the engine is revved to full throttle to simulate rapid acceleration. Vehicles with peak smoke density or opacity above 55 percent, nearly equal to their emissions when they were new, would be cited. Owners would have 45 days to repair the vehicles to lower smoke emissions, equal to the time limit for fixing safety problems under an existing CHP program.

First-time violators of the standards would also be subject to a minimum $300 fee, initially proposed by the trucking industry, to fund research aimed at developing cleaner diesel fuel. A second violation within a year could result in fines as high as $1,800.

ARB research has shown the greatest causes of excessive soot from diesels is tampering with engine components to increase acceleration and neglected maintenance. In a pilot program, the ARB found the average repair cost to lower emissions was $500, which is similar to repair costs under the Smog Check program when the $100,000 price tag for big trucks or $20,000 for an engine is considered.

"With these random, roadside tests, we are asking truck and bus operators to do no more than what owners of gasoline-powered cars have done since 1984 through the Smog Check program," noted Jananne Sharpless, ARB chairwoman.

The ARB has set other programs to control emissions of soot-like particulate after research documented the unique health hazards they pose. According to the research, diesel particles are small enough to bypass the body's natural filtering system and cause tissue damage deep in the lung. In addition, they can be carriers of potentially cancer-causing compounds, including dioxin and benzene.

The proposed roadside test is the third major ARB program to control diesel soot. ARB tailpipe standards will make 1991 model buses and 1994 model trucks "smokeless" and clean-up standards for diesel fuel, which will go into effect in 1993, will reduce emissions from existing vehicles by as much as 25 percent.

Sharpless noted that, besides their health hazard, diesel emissions are the single largest source of public complaints that the ARB receives about pollution. A Southern California program in which smoking trucks receive citations from the CHP generates 10,000 complaints a month.