A U.S. federal government report forecasts that the overwhelming majority of cars on American roads will still be powered by gasoline for some time.

The U.S. Energy Information Administration Annual Energy Outlook report for 2014 isn't all bad news. Though it forecasts that only 1 per cent of all new cars sold will be of the plug-in electric variety, other fuel efficient or alternatively powered vehicles will become progressively more popular in coming years.

Chief among these will be hybrid vehicles that combine a small petrol or diesel engine with an electric motor to cut emissions and optimize fuel economy -- cars such as the Volkswagen XL1, the only car currently capable of traveling 100 kilometres on 0.9 litres of fuel, launched earlier this year.

Hybrids could account for 5 per cent of all new cars on the road by 2040 and already have a 3 per cent market share.

Thanks to the kudos associated with Audi, Mercedes and BMW, U.S. consumers are also starting to change their opinion about diesel engines.

They're no longer the noisy, dirty and slow motors they once were and this image rehabilitation will help to drive sales. In 2012, only 2 per cent of new cars sold in the U.S. were diesels, but they are expected to account for 4 per cent of all new vehicle sales by 2040.

Currently 18 per cent of all new cars on U.S. roads are powered by something other than gasoline; by 2040 they are predicted to represent 22 per cent of all new cars. However, that means that even two and a half decades into the future, three-quarters (78%) per cent of cars will be powered solely by fossil fuels.

Still, the nature of traditionally powered cars is also changing, even in the U.S. Car makers are slowly moving away from big-block V8s to smaller, four-cylinder engines. Companies such as Ford are using turbochargers to squeeze both power and efficiency out of low-capacity engines.

The report also estimates that 42 per cent of gasoline-fueled cars will use some form of battery-powered stop start or energy regeneration technology to boost power further while continuing to cut emission and increase fuel efficiency.