The California Air Resources Board amended its regulations targeting diesel emissions last week, in some cases extending deadlines for compliance, but in some cases making rules stricter.

Even with the amended regulations in place, diesel particulate matter emissions will be reduced from today's levels by 50 percent by 2014 and 70 percent by 2020, CARB said in an announcement.

Over the past year, CARB staff held 20 public workshops throughout the state to discuss options for revising diesel control measures affecting commercially owned trucks, buses, port trucks, tractor trailers and off-road vehicles. As a result of concerns about how the regulations are affecting businesses already strapped by recession, the board made several changes.

Statewide On-Road Truck and Bus Regulation

Approved in December 2008, this regulation will clean up emissions from the nearly 1 million heavy duty diesel trucks that operate in California. Amendments, CARB said, will reduce overall compliance costs by about 60 percent. It will delay the initial compliance date for the retrofitting of heavier trucks and allow them to operate another 8 years before being required to use a truck that meets 2010 emissions standards. It also expands credits for fleet downsizing, adding cleaner vehicles ahead of any regulatory requirements, and for installation of early retrofits.

Port Truck Regulation:

Approved in December 2007, the port truck (or "drayage") regulation has already banned pre-1994 trucks from the ports and started requiring retrofit diesel particulate filters on others earlier this year. The amendments close a loophole that had excluded Class 7 trucks, which now will be required to have DPFs by 2014. It also will expand the regulation to include trucks operating outside port or rail yard properties to prevent non-compliant trucks from receiving cargo from clean trucks in those areas.

Heavy Duty Diesel Greenhouse Gas Reduction Measure

This rule requires trucks operating on California highways, whether or not the fleet is domiciled there, to use equipment that is U.S. EPA SmartWay certified or retrofitted with SmartWay-verified aerodynamic devices and low-rolling-resistance tires. The changes extend the deadline for installation of low-rolling-resistance tires by one year on pre-2011 model year tractors and four years on pre-2011 model year trailers. They also exempt open shoulder drive tires, allow an optional second trailer retrofit compliance schedule for large fleets, and provide additional reporting flexibility.

There are now exemptions for storage trailers, and some relief in certain situations, such as relocation of long-haul trailers, transfer of trailer ownership, and trailers that enter the state no more than once a year. 2009 model year refrigerated van trailers get a delay in the compliance provision, as well as certain trailers for which SmartWay-verified technologies currently aren't compatible.

For more information, call CARB's diesel emissions regs hotline, 1-866-6DIESEL.