US President Barack Obama is expected to introduce new, national standards for reducing automobile emissions and improving fuel efficiency today, thanks to a milestone agreement that has broad support among environmentalists, the auto industry and consumers.

Under the new rules, passenger car efficiency will reportedly increase from the current 27.5 miles per gallon (mpg) to 42 mpg by 2016. For light trucks, the current 24 mpg standard will be raised to 26.2. Collectively, the new standards are expected to reduce global warming emissions from new vehicles by 30 percent.

Details of the plan remain somewhat murky, with various news outlets reporting different and somewhat contradictory information in advance of the announcement.

Most seem to agree, however, that the new standards are based-upon — and will, for the time being, supersede — the aggressive emission standards proposed by California and 13 other states, all of which were stricter than existing US national standards.  The tougher, state standards would have required a waiver from the US Environmental Protection Agency before taking effect., and although similar waivers had been approved dozens of times in the past, they were denied by Bush administration, leading Congress to set a June 30 deadline for the Obama administration to resolve the matter and comply with a 2007 law requiring a 40 percent improvement in vehicle efficiency by 2020.

The new standards are expected to comply with the Congressional mandate, and lawsuits filed by the auto industry challenging — and delaying — implementation of the different state standards will also be dropped under the new agreement.

According to Grist:

The announcement will also be an opening move for the EPA in its fight against global warming.  Last month, the agency indicated that it intends to begin regulating greenhouse-gas emissions under the Clean Air Act, having determined that planet-warming gases threaten human health. EPA’s first target was expected to be mobile sources—i.e., cars and trucks—which account for 20 percent of all U.S. emissions.

Meeting the new standards is expected to increase the cost of a new vehicle by $600-700, an amount that will be offset by decreased fuel costs for the higher mileage vehicles.