Motorists should be taught new driving techniques to reduce carbon emissions from their vehicles, a report suggests.
Car emissions depend on how a vehicle is driven
A report by the Commission for Integrated Transport also suggests new rules to ensure drivers can only buy the most fuel-efficient cars.
It also wants new cars to be as environmentally friendly by 2020 as the greenest cars which are currently available on the market.
The CfIT is the body which advises the government on transport.
BBC transport correspondent Tom Symonds said cars and lorries are the biggest source of carbon emissions in the UK.
Lowering car windows increases fuel consumption
Consumption is also increased by driving with a roof rack on the car
Turning on air conditioning uses 10% more fuel, producing more CO2
To cut emissions, drive smoothly by being gentle on the accelerator and stopping without a jolt
Driving at 80mph produces a third more CO2 than driving at 70mph
The CfIT believes that motorists can be taught to drive more cleanly, saying that keeping to 70mph rather than 80mph on the motorway will cut emissions by almost a third.
It suggests having state-sponsored lessons in eco-motoring for the nation's drivers and wants all cars to produce no more than 100g of CO2 per kilometre by 2020.
The report also says speed limits should be more rigorously enforced, and other advice includes turning off air conditioning, driving without a roof rack and generally driving with a "lighter touch".
Research suggests that using a car's air conditioning consumes 10% more fuel, which has the effect of producing CO2.