To significantly affect fuel consumption in the near-term, we shouldn't put all our eggs in the hydrogen fuel cell basket, according to Professor John Heywood
at MIT. It could take more than 50 years for fuel cell vehicles to have a significant effect on fuel consumption, even though it is estimated competitive fuel cell vehicles will be available within 15 years. After the fuel cell vehicles become available, it will take decades to affect fuel consumption, as they work their way into the market. If the fuel cell cars follow the path of hybrid vehicles, it could take roughly 25 years for these vehicles to make up about one third of the new car and light-truck sales. Advances to internal combustion engines continue to happen, are available in the marketplace faster, require less retooling and therefore spread through the fleet faster. Short-term changes in fuel consumption need to be realized with existing technologies, and changes in vehicle usage and consumer buying patterns.
[Source: Technology Review]