If we were starting from scratch and creating an infra structure around hydrogen it would be perfectly plausible. The biggest issue is getting hold of the hydrogen. There is plenty of it about and we can make as much as we want but it takes energy. There are plenty of renewable energy sources the can be used to harness hydrogen but launching something so large takes money. The only people with enough money are the oil companies, the very people who don't want their oil to be devalued by new technologies. New transporters, new fuel stations etc all at great cost which would be passed on to the relatively low volume user. Just like electric cars people can't afford the alternative and it fades away.
there are 2 current forms of viable hydrogen use in motor vehicles. One as a combustible fuel and one as a source of electrolytic reaction to power electric vehicles, sort of an on board fuel tank for batteries. Both have the same issues regarding infrastructure. It is possible to buy small hydrogen cells to add to your internal combustion engined car which it is said to improve economy and efficiency. In theory it looks good but having conducted test on the rolling road, real world fuel consumption and using wide band lambda readings in a series of vehicles in several different applications I'd have to say I haven't been able to see any consistent improvements from using the units. They do definitely produce hydrogen though so there must be some mileage in a proper system.
Ultimately I believe the market must adapt for alternative fuel cars. A 2 car family would probably find itself with an electric car for local journeys and a combustible fuelled car for longer journeys. Bio-diesel and bio-ethanol are also alternatives to hydrogen but again have similar problems. We have already done studies into bio-diesel and are currently registering with HM revenue and customs to allow us to acquire some ethanol for testing. At £3 a litre though it may be a while before the general public want to put it in their cars!
