Diploman;
There are a number of electric cars in the works.
Nisson/Renault, Toyota, GM and now Ford.

The idea of a small petrol motor is to extend range by starting it
when the battery charge falls and the continuous running motor
operating at its best efficiency will charge the battery and get ahead
of the discharge rate in stop start traffic, but on a long trip may
require you to drive at a slower speed.
So you have those rest stops they are always
recomending and the engine charges it up if you can't find a power point
to plug into.

Belly is right, public transport cannot take up the load.
In Sydney it will be impossible to get enough passenger trains through
Hornsby because of the very much increased freight traffic that will
occur as the truckies go broke.

It appears that 75% of commuters travel by car.
I can't see a three times increase in trains & busses.

The Ford electric car story however is worth looking at.
They killed the EV1 a car we could have been driving now but the more petrol rises the closer we are to new fuels.
Ten years from now oil may be much cheaper , while we will run out one day its not yet.
World wide we are headed for real use of other fuels and oil prices has helped get us started in new directions.