DaimlerChrysler AG unveiled an environmentally friendly compact car that turns hydrogen gas into electricity and leaves just a stream of water vapour for exhaust. But don't expect to be able to buy anything like it until 2004 when the company hopes it has brought down production costs and encouraged the distribution of suitable fuels. The NECAR 4, driven onto the stage of a Washington press conference by the company's two top executives, solves many of the weight and space problems of previous prototypes. Based on the Mercedes A-Class small car, the five-seater NECAR 4 can travel 280 miles before refueling. Its NECAR 3 predecessor unveiled in 1997 could carry only two people 250 miles because a mass of plumbing took over the back seat.