Owners of model year 2003 and older reefer engines that met low-emission reefer standards will get an extra year to meet a future standard.
The agency has amended its Transport Refrigeration Unit Airborne Toxic Control Measure to allow 2003 engines to meet a less stringent standard.
California Air Resources Board will enforce the January compliance deadline, but will consider an option for meeting the standard.
An appeals court rejected a challenge by the American Trucking Associations and the Truckload Carriers Association.
The California Air Resources Board issued about 100 citations during the first two weeks of enforcement.
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