Just to point out that H2 cars have been here awhile. Simple to modify a car. Just get rid of the carburetor, replace gas tank with carbon fiber tank full of 5,000 to 10,000psi hydrogen. Then regulate that pressure down to less than 20 psi and put that right into the manifold where the carburetor was. Change the timing to top dead center and there ya go. The first internal combustion engine was designed to run on a hydrogen dominated gas in the 1800's. All the explanations of igniting the gas at top dead center are not true for gasoline. Gasoline burns too slow for this, so they have to ignite before the piston gets to the top. This means that the piston is fighting against an ever expanding gas as it moves up. This wastes lots of energy as heat. They took a good idea for an engine and bastardized it to work on gasoline. Back then compressed h2 just wasn't practical. Now, any welding shop will sell you compressed hydrogen.
Here is a car that was modified in the 70's. http://www.wired.com/cars/energy/news/2004/09/65080