Just make some cars with coaxial axles that generate electricity in the same way as hydro turbines. Do the same with the drive shaft too. They're all turning most of the time unless you're stuck in beltway traffic. Or has that already been done? I seem to remember hearing about one hybrid car that recharges when you brake but nothing in the way of how it generates power. Maybe raise the driving age to 18 too, but I doubt parents want to drag their kids everywhere when the kids could do it themselves.
All cars use a belt-driven alternator driven off the crankshaft.