Considerable advances have been made in recent years in the field of hydrogen-air fuel cells, and plans are already being made to use such power generators for urban transportation. This is shown by a study of the possibility of equipping a vehicle of the Renault 4L type with a hydrogen-air cell. This paper describes a detailed study of such an installation. The weight of the power source is acceptable, as are the rates of acceleration. A speed of 80 km/h (50 mph) can be sustained continuously, and an autonomy of between 230 and 560 km (143 and 348 miles) can be attained depending upon the speed of the vehicle, with an effective load of 340 kg (750 lb). Two important obstacles (power source and use of hydrogen) are in the process of being solved by using inexpensive materials and by storing hydrogen by means of hydrides. Thus, the hydrogen-air fuel cell should be a decisive contribution to the use of electric vehicles, and its influence could become even greater if, on a long-term basis, the trend to make intensive use of hydrogen as an energy extension is confirmed.