SACRAMENTO – The California Air Resources Board (ARB) today adopted a diesel air toxic control measure that requires big rig truck and interstate bus operators to shut their engines down after five minutes of non-essential idling.

ARB Chairman, Dr. Alan Lloyd said, "This new measure expands our control over diesel engine emissions by cutting an obvious source of this pollution.  Modern diesel engines and new, cleaner fuels do not have to be operated differently than other types of engines, which owners simply turn off when they are not in use."

The new regulation affects the more than 400,000 heavy-duty diesel trucks and buses registered in California and all out-of-state trucks and buses operating in California. The regulation will eliminate 166 tons of particulate pollution per year and about 5,200 tons per year of smog-forming nitrogen oxide emissions from the state's air. As a result of the new measure, California truck and bus operators will each save about 125 gallons of diesel fuel per year, or collectively over one million gallons each week. Bus operators may idle for ten minutes prior to entering passenger service in order to prepare their vehicles for customer use.

The new measure is similar to the ARB's school bus idling measure adopted in 2002 that prohibits any unneeded idling. The new measure allows idling for up to five minutes but like the school bus measure limits idling within 100 feet of residences and will take effect almost immediately. The penalty for violating both measures is $100 per violation.

Diesel operators often let their engines idle for long periods of time because of fears that their vehicles might not start well when cold or in bad weather. However, newer engine and fuel technologies have eliminated that problem. As part of the new regulation's enforcement efforts, the ARB will institute a public education program to help diesel drivers better understand the newer technologies and how they can improve vehicle operations.

This measure is the latest in an ARB program to reduce the toxic risk from diesel exhaust. In addition to the school bus idling measure, the ARB has also adopted rules that limit emissions from urban transit buses, garbage trucks and portable engines. In conjunction with U.S. EPA, the ARB has also approved standards for low sulfur diesel fuel set to take effect in 2006 and stringent tailpipe emission standards, which become effective in 2007.

ARB research has shown that diesel exhaust accounts for 70 percent of the toxic air contaminants that Californians are exposed to daily. The ARB identified diesel exhaust as a toxic air contaminant in 1998.