While the U.S. government has implemented a fleet-wide fuel efficiency standard of 35mpg by 2020 for carmakers (plus an interim mandate of 31.6mpg by 2015), California is planning to implement its own ruling of 36.8mpg by 2016. The issue has been a major headache for carmakers as California represents the single biggest market for new vehicles in the whole of North America and to make matters worse 13 other states plan to copy the stricter mandate.

Although the Bush administrations has so far blocked the strict rules set by the California Air Resources Board (CARB), all three current presidential candidates support the idea. The auto industry has publicly voiced its concern over the difficulty in meeting a 'patchwork' of regulations across the different states and even plans to meet with California Governor Arnold Schwarzenegger to warn of the effects of the tougher standards.

The CARB has since responded, stating that it is open to considering a regional framework of regulations rather than a state-by-state basis, reports The Detroit News. Just what a 'regional' framework would entail is yet to be seen, but presumably it will allow the manufacturers some breathing room in attempting to meet the differing regulations.

Dave McCurdy, president and CEO of the Alliance of Automobile Manufacturers, has stated that state-specific regulations are too difficult to conform to, and that a national approach should be undertaken. McCurdy also stated that while CARB rules were likely to come in with the election of the next president, auto manufacturers were open to using California as a testing ground for future technologies - but insisted that other than this there should be a national framework of legislation to regulate emissions.

President of CARB, Mary Nichols, has countered this by stating that the demands of the CARB rules are already within industry reach and should only require a "little creative repackaging" to achieve.