American carmakers have launched EcoDriving - a nationwide initiative to help drivers there reduce fuel use and cut CO2 emissions.

The initiative involves teaching similar driving techniques to those taught to fleet drivers by eco-driving schools.

"You can save money and save the environment by driving green," said Dave McCurdy, president of the Alliance of Automobile Manufacturers.

“By following a set of subtle and easy-to-use best practices for driving and vehicle maintenance, a typical EcoDriver can improve mileage by about 15%.”

He said that if all Americans practiced EcoDriving, it would be equal to 450 billion miles travelled on its roads without generating any CO2 emissions.