hydrogen dangerous??You must be kidding, you don't think 15 gallons of gasoline isn't dangerous. Gasoline is used as a fuel because it has one of the highest energy densities of all. Properly mixed with air, gasoline has many times the explosive power of hydrogen. Indeed, hydrogen, despite the Hindenberg incident, is actually very safe.
The reason pure hydrogen is desireable is not its energy density but is lack of byproducts, when you oxidize hydrogen in the right way, you get water, either as a fluid or a vapor. Gasoline produces all sorts of nasty byproducts, primarily because of the carbon and incomplete oxidation.
Hydrogen will have its day and soon. Just a matter of making it worthwhile to scrap all that gasoline hardware, which amounts to $Billions. Going to take a while before they can depreciate all that stuff.