French inventor Guy Nègre took three years to perfect a motor which runs on compressed air. In trials, the motor powered a Citrðen chassis for ten hours with a top speed of 60mph. Now it has been adopted by the Mexican Government, who hope to replace all of Mexico City’s 87,000 petrol and diesel taxis eventually but are starting with a 40,000 production run by the organisation DINA, a Government licensee

• Not only does the engine run on air. As it drives along, the motor's carbon filtering system can suck in polluted air and breathe out clean air

• The 300 litre compressed air tank can be refuelled in three minutes using a high pressure compressor, or in four hours using a domestic version. The latter would cost about £1 in electricity

Guy worked with racing cars for 30 years, which use compressed air to start up.

For more information: Guy Nègre, CQFD Air Solution, Forum Aurélia, 83 BRIGNOLES, France. Tel.: 00 33 49 80 51 000 Fax 00 33 49 46 95 391