Cars are becoming increasingly cheaper to buy and their numbers around the world are growing fast. The energy required to make them all move is huge and difficult to replace without fossil fuels, the maths indicate we actually have no access to any other energy source great enough. I think we will do lot more walking and catch the bus/train more often in the long term future.

In the short term, gas fuels like LPG and natural gas, as well as electric engines are going to be popular, but not sustainable for very long. Hydrogen will never happen - providing nobody finds a clever new way to make it with very minimal energy input. The chances of this are low, very low. You'd need to cheat physics, which has been done, but not too often. Nice when it happens, just don't count on it.

I really don't see how the energy-hog car can survive as world population increases and our energy reserves reduce.

the petro fuel internal combustion engine is the past, not the future - good to make it as efficient as possible for the short term, but what's really needed is a more wholistic mindset on the lifestyle of our [western] culture - get away from the "need" for constant travel ..... and start walking more for your healths sake

Bill