The car that runs on air.

[Jan and Scott]

An engineer has promised that within a year he will start selling a car that runs on compressed air, producing no emissions at all in town.

The OneCAT will be a five-seater with a fibre-glass body, weighing just 350kg and could cost just over £2,500.

It will be driven by compressed air stored in carbon-fibre tanks built into the chassis.

The tanks can be filled with air from a compressor in just three minutes - much quicker than a battery car.

Alternatively, it can be plugged into the mains for four hours and an on-board compressor will do the job.

For long journeys the compressed air driving the pistons can be boosted by a fuel burner which heats the air so it expands and increases the pressure on the pistons. The burner will use all kinds of liquid fuel.

The designers say on long journeys the car will do the equivalent of 120mpg. In town, running on air, it will be cheaper than that.

"The first buyers will be people who care about the environment," says French inventor Guy Negre.