SACRAMENTO - The California Air Resources Board (ARB) today approved inspection programs to control air emissions from heavy-duty trucks and buses that run on diesel fuel.

        "This is a major step toward further improvement of California's air and a step that will bring long overdue air quality responsibility to heavy-duty diesel vehicles, similar to that already borne by passenger car emissions," said John Dunlap, ARB Chairman.

        Dunlap pointed out that unlike gasoline-powered passenger cars and light trucks which are subject to routine "smog checks", diesel trucks and buses have not had any type of routine inspection program to be sure they meet air emission standards since 1993, the last time heavy-duty vehicle inspection programs were operated in California

        While heavy-duty diesel trucks and buses make up about 2 percent of the state's on-road vehicle fleet, they contribute about 30 percent of the oxides of nitrogen that come from the on-road fleet. Oxides of nitrogen are one of the main contributors to ozone. Ozone contributes to respiratory diseases such as asthma, bronchitis and emphysema.

        In addition, diesel vehicles contribute about 65 percent of the small particulate matter known as PM10, which also contributes to respiratory disease and is suspected of causing cancer and birth defects.

        "We are gratified to see that major trucking industry representatives, such as the American Trucking Association and the Engine Manufacturers Association, have shown their concern for California's environment by supporting this program," said Peter M. Rooney, California's Secretary for Environmental Protection.

        An exact date for the start of inspections, which will be carried out at California Highway Patrol weigh stations and other locations that will not impede traffic flow, has not been selected. However, the program is expected to begin by mid-1998. When it is fully implemented, the inspection program will remove about 23 tons of pollutants a day from California's air.

        Inspections are done by using a measuring device to check the opacity or darkness of the smoke coming from the vehicle exhaust system. Pre-1991 engines that generate smoke with an opacity of 55 percent or greater fail while 1991 and newer engines fail with an opacity of 40 percent or greater. Pre-1991 vehicles which measure between 55 percent and 69 percent opacity will be issued fix-it tickets, but will not be fined.

        While the program allows for "fix it" tickets to be issued in some circumstances, the bulk of the violations will result in a $300 fee, used to fund clean diesel engine research, for a first violation that is corrected within 45 days. The fine goes to $800 after 45 days and $1,800 if a second or subsequent citation is issued within one year.

        School buses are exempt for the $300 fine if the violation is corrected within 45 days. The inspection program will apply to all heavy-duty diesel vehicles in California, even if they are from out of state or from another country.

        Under the fleet inspection program, which is a companion program to the roadside inspection program, fleet operators are required to have their vehicles inspected yearly as part of normal maintenance and to repair any trucks that do not meet the emission standards.

        ARB research has shown that excessive smoke from diesel vehicles generally results from not properly maintaining the engine's fuel system or because of deliberate tampering with the engine.