I drove 1800 miles in a Hydrogen Car

Why fuel cells is pretty obvious. If you are driving between cities or states ... you wouldn't have to rent a motel while you recharge your car. It's one of the biggest criticisms of battery cars. If something like this was affordable and standardized at every gas station it would be pretty awesome.
What would also be awesome is a combustion engine that can use fuel other than gas that burns cleaner. Low income people won't be able to afford to buy a fancy new Tesla and the like so there is that to. So a clean burning fuel that can work in existing cars would be a good transition point.  But the biggest obstacle and nobody has really took this on ... the infrastructure is not in place enough for most of this.