With the rise in diesel popularity among light trucks, and the recent tightening of emissions regulations on new heavy-duty diesel engines, recent moves to tighten emissions regulations in California have attracted attention. The state of California reportedly requested a waiver from federal preemption over a state engine emissions standard. Industry groups says that the request could force large numbers of trucks to comply nationwide. The National Academy of Sciences (NAS) is expected to issue a long-awaited report which will address California’s authority to set transportation emissions standards that are stricter than the rest of the country. The report is expected to examine the ability of other states to subsequently adopt California rules. Critics of the waiver say California’s authority is outdated and the state should be forced to conform to national standards. However, California has long argued its power to set standards is necessary because of the state’s severe air quality problems that stem in large part from transportation. Groups recently filed public comments on California’s request to the U.S. EPA last year for a waiver to implement a regulation on diesel powered transport refrigeration units. The California Air Resources Board (CARB) originally approved the rule in 2004, with implementation to be phased in beginning at the end of 2008. In February, the American Trucking Associations (ATA) filed comments criticizing the rule for placing the burden of meeting the requirements on truckers, instead of engine manufacturers. In its waiver request submitted in March 2005, however, CARB argued that the rule was critical for reducing harmful emissions of diesel particulate matter from the refrigeration units. The state argues that a rule is necessary because EPA is only allowed to promulgate federal standards for new diesel engines, and not engines already on the road. According to sources, the NAS report is expected to be released on March 16.