Car makers and their key union appear to have won the first round of a battle to improve light vehicle fuel consumption in the United States.

A bi-partisan Senate proposal championed by Democratic senator John Kerry of Massachusetts, wanted to boost economy by up to 50 percent over 15 years, making 36mpg consumption compulsory for all vehicles.

But the proposal has not attracted enough support though there has been considerable opposition from the vehicle makers, United Auto Workers union and other senators, particularly those from car-making states.

An alternative plan put together by the Democratic senator for Michigan, Carl Levin, and likely to get a pass vote as part of a wider energy bill in the Senate today, gives the US National Highway Traffic Safety Administration (NHTSA) 15 months to put together a new Corporate Average Fuel Economy (CAFE) standard for light trucks and two years for cars.

The standards would have to take into account 13 factors including vehicle safety, manufacturer competitiveness and effects on employment but leave the setting of new CAFE figures to the NHTSA, rather than the Senate.

Opponents had cited the proposals as sounding the death knell for the huge SUVs and minivans American drivers like so much.

The rising popularity of such vehicles, which have less stringent fuel economy requirements under current CAFE rules, has kept the average economy of the American fleet at about 1988 levels, despite advances in vehicle technology.

As usual in America, debate has been furious with opponents bombarding senators with ads and furious lobbying

Honda, which pretty much agreed with the Kerry proposals but ending up siding with the Levin alternative, was accused of having an unfair CAFE advantage because it sells fewer trucks than US makers. Senators opposed to the tough new standards claimed farmers would need to swap huge pick-ups for golf carts.

Republican senator John McCain of Arizona argued that if Ford was already advertising 40mpg economy for its hybrid Escape SUV, above the proposed 2015 CAFE requirements, the industry didn't have a problem. He scathingly referred to previous claims that compulsory seatbelts, improved economy and airbags would signal the end of the vehicle industry - but didn't.

Both sides do however agree with the National Academy of Sciences report that concluded that fuel economy improvements, including gains of as much as 42 percent on SUVs and minivans, are already achievable without sacrificing size or horsepower, using existing technology.

The main disagreement appears to be over the amount of lead time vehicle makers are given.

The study said that vehicle makers would otherwise have to make smaller, lighter vehicles with reduced safety as was the case in the late 1970s and 80s.