Re: Cars of the Future.
I think hydrogen is a promising fuel however it has a major problem in that it explodes in air at a concentration of anything between 5% and 95% - ie any slight leak or air ingress can be catastrophic.
Compare that to, for example, LPG with explosive range of 2% to 10% in air
BTW those figures may not be exactly right as I am going from memory but they are very close. Technically they are called Upper Explosive Limit (UEL) and Lower Explosive Limit (LEL) if you want to look them up.
Hydrogen has to be very carefully monitored when it is used - it is a coolant in Electricity Alternators over 50MW for example - and must have emergency de-gass procedures in place if the concentration gets below approx 98%.