California Air Resources Board

SACRAMENTO – A new program to inspect heavy duty diesel trucks and buses for excessive smoke is underway in California. The inspections, carried out by the California Environmental Protection Agency's Air Resources Board (ARB), will be conducted at California Highway Patrol weigh stations and other roadside locations which won't impede the flow of traffic.

        Pointing out that gasoline-powered passenger cars and pickup trucks have been subject to routine Smog Checks since 1984, ARB Chairman John Dunlap said, "Mindful that California still has the nation's most unhealthy air quality, this inspection program for heavy-duty diesel vehicles significantly advances our clean air goals for the next century.

        "Trucks and buses, like the millions of cars on the road, are now expected to keep their engines running well to minimize emissions and maximize the effectiveness of our clean-air strategy for mobile sources," said Dunlap.

        The ARB inspection program is supported by many trucking industry organizations, from the American Trucking Association and the California Trucking Association to small owner-operators.

        A related program, the Periodic Smoke Inspection Program, also begins July 1, 1998 and requires fleet operators to self-inspect their trucks once a year and repair any vehicles that do not meet the emission standards. When fully implemented, the two programs will remove about 24 tons of pollutants a day from California's air.

        Dunlap also pointed to recent action by Governor Pete Wilson to stimulate replacement of older diesel engines through $50 million in grant funding as a means of motivating the switch to cleaner engines. The grants would be used to offset the incremental cost of purchasing cleaner engines in the course of business. "This incentive-based program taps into new environmental technologies for clean diesel or alternative-fuel engines that will provide a public benefit through cleaner air sooner than we otherwise expect from existing regulatory deadlines," said Dunlap.

The Statistics

        While heavy-duty diesel trucks and buses make up about two percent of California's on-road vehicle fleet, they contribute about 30 percent of the oxides of nitrogen (NOx) that come from the on-road fleet. Nitrogen oxides help form ground-level ozone, one of the most health-damaging components of smog.

        In addition, diesel vehicles contribute about 65 percent of the small particulate matter known as PM10 that comes from on-road vehicles. PM10 contributes to respiratory disease by lodging deep in the lungs and is suspected of causing cancer and birth defects.

The Details

        ARB inspectors will use an electronic device to measure the opacity, or darkness of smoke, coming from a vehicle's exhaust system. Pre-1991 engines that generate smoke with an opacity of 55 to 69 percent get a "notice of violation" (NOV), similar to a fix-it ticket, while pre-1991 engines that test at 70 percent or higher receive a citation. Operators receiving an NOV must make needed repairs and submit proof of correction to ARB within 45 days or receive a citation and face an $800 fine.

        Engines from 1991 and newer fail with an opacity reading of 40 percent or greater and receive a citation. The citations result in an $800 penalty for a first violation, of which $500 will be waived if repairs are made within 45 days and a demonstration of correction submitted to ARB. The full $800 must be paid if repairs are not made within 45 days. After 45 days, if the problem is not repaired and the truck is checked again, the penalty for a second violation goes to $1,800 plus the still-pending $800 from the first violation for a total of $2,600. Fine money goes to fund research into cleaner diesel engines and cleaner diesel fuels.

        School buses are exempt from fines if violations are corrected within 45 days. The inspection program applies to all heavy-duty (6001 pounds or heavier) on-road trucks and buses in California, even if they are from out of state or from another country. Research has shown that excessive smoke from diesel vehicles generally results from improper maintenance of the vehicle's fuel system or because of tampering with the engine.

        An ARB study of 68 trucks that were emitting excessive smoke resulted in an average repair cost of $639 to bring the vehicles into compliance with the new smoke standards. Getting trucks into compliance resulted in extended engine life and improved fuel mileage. It is estimated that approximately 17 million gallons of diesel fuel are wasted each year in California by trucks with fuel systems that are not maintained to manufacturer specifications.