DaimlerChrysler engineers first succeeded in making the fuel-cell drive so compact that it would fit into the sandwich-construction floor of the A-Class in 1999, when the 70-kW NECAR 4 came out. Powered by liquid hydrogen, this latest model had a top speed of 145 km/h and could drive for 450 kilometres on a single tank of fuel, while it also had enough room for five people plus luggage. The NECAR 4a was specially built to be used in the fleet…