Hybrids will not be enough to comply with new US tailpipe standards

Department for Standard confirms plans to impose strict new fuel efficiency standards on auto industry as experts warn major overhaul of car design is required

The US Department of Transportation has proposed a new interim milestone designed to reinforce fuel efficiency standards legislated in December.

In a speech this week, transportation secretary Mary E Peters proposed fresh fuel efficiency standards for vehicles built between 2011 and 2015. Passenger automobiles will need to achieve a fuel efficiency rating of 35.7 miles per gallon (mpg) by 2015, while non-passenger vehicles, including light trucks, would need an average fuel economy rating of 28.5 mpg. On average, that represents an increase of 26 per cent over today's fuel efficiency requirements.

Peters also announced a more aggressive schedule for implementing the-so called CAFE tailpipe standards than many automakers expected. The secretary's proposal is now subject to a 60-day commentary period, and the Department hopes to have a rule in place by the end of the year.

Bill Van Amburg, senior vice president at Calstart, a non-profit organisation dedicated to producing cleaner transport, suggested that manufacturers would not be able to rely purely on hybrid engines to hit the new targets.

"To get the fleet average reduction needed, automakers will need a complete portfolio of strategies and technologies, and many of them combined in certain cars," he said, adding that the US government was following, rather than leading, in its policy making and that fuel prices were already moving the market towards more efficient vehicles. "Clearly, there are things that can be done to squeeze a lot more out of conventional systems, from turbocharging to displacement on demand to lighter-weight materials."

However, Charlie Territo, spokesman for the Alliance of Automobile Manufacturers, said serious concerns remained about the cost of such measures, claiming that the rules will cost the auto industry $47bn (£23.8bn) and could increase the price of many vehicles. "Whether or not manufacturers meet these standards will depend not only on whether they can implement new technologies, but on whether consumers can pay for them," he said.