The problem with hydrogen, apart from it being highly flammable, is that it takes so much energy to extract into its elemental product. It's always attached to something else. So whilst it is clean at the point of use, it's actually pretty poor when the production chain is considered.
Battery technology is coming along. Who remembers the days when it would take 3 hours to charge their Nokia 3310? It was a 900mAH battery. Now we have phones that charge in less than an hour and have 4 or 5 times the battery capacity. But the problem that plagues hydrogen also affects batteries. They're very dirty to produce. And coal makes them very dirty to charge!
So the above two, whilst they make towns and cities nicer, also kill the planet just fine too.
Diesel's days are numbered. I suspect that large goods vehicles will keep diesel for now but will eventually use batteries, once capacity issues are resolved. Torque is available in bucket loads on electric vehicles so they are perfect for haulage.
My gut feeling is that petrol power will be the predominant car based option for a while - larger engines minus turbos though. Drilling out oil is generally cleaner than the production line for batteries and hydrogen. But I think technology to capture emissions will progress. I can imagine a day where we fill up with petrol and have interchangeable filters that we drop off at petrol stations.
This leads me onto my next thought. If battery technology progresses enough to make them small but still slow charging, can we imagine having battery stations where we get fully charged battery packs and swap them over in a minute or two? All it'd need is a standardised battery. And clean production line and charging!
The major obstacle to electric cars in their plug in form though is modern city life. Electric vehicles are good for getting pollution out of cities, although this is actually just displacing it. However more people in cities are living in flats than houses now. This means communal car parking or street parking. I'm certain that my freeholder will not be cooperative if I were to ask them to install charging points in the car park! The cost of doing this would be staggering. Especially for all 28 flats where I live. Same with streets and councils.
Self driving will probably become mandatory for new cars. I suspect within the next 20-30 years once the new European form of GPS is in full use. Current GPS provided by America is good for sat nav but it's not able to pin point down to the foot or so necessary for more difficult navigation tasks. The potential road safety argument (and the one government will want - control) make self drive inevitable though. It also theoretically will help with congestion.
