I think some of the discussion about alternative energies (namely hydrogen) seems to be leaning towards the fact that people think that this is going to (for some reason) HAVE to be a rapid (almost overnight) change. There is no reason why hyrdogen, petrol, and deisel fuled cars can't be on the road with one another for dozens and dozens of years. If we did move to hydrogen, I don't see there being a ban on "fossil fuel" cars. Think of it like you do the seat belts laws. Cars that were built before seat belts were required can still be legally operated to this day. I don't see why this CAN'T be done with hydrogen fueled cars. Run your petrol/diesel cars until they run no more, but all that can be manufactured must be hydrogen. To be frank, changes probably wouldn't even be THAT fast. Likely changes would start with car manufacturers having to make a certain percentage of their cars be hydrogen vehicles. This percentage would rise slowly every couple of years until the goal of 100% is reached.
FWIW I am not necessarily advocated hydrogen fuel. If you wish, insert "alternative fuel" in anyplace you see me write hydrogen. I only used hydrogen since that seems to be the hot topic.
Also, finding alternative ways to gather and even produce petrol and diesel sound great. I personally am in no way against that. That said, I think NOTHING is a sure thing just yet other than what we have in reserves, so it's certainly not a bad idea to spend time and money researching various technologies.
I, for one, would be an advocate for alternative energies simply because we, as a nation, could hopefully stop relying on other nations for this energy as we may be able to produce much or all of it right here in the good old USA. This would keep the money flow within our own borders as well as produce many jobs.