All you need is a shaft to turn a pulley. Many arrow signs use a small gaso/diesel engine to turn a pully and drive a Motorola alternator to charge the battery banks.
I know this is a meme/joke picture, but that's an incredibly inefficient source for the turning of the alternator. The car engine turns at a significantly faster pace than your tire ever would. Though I'm sure someone in the Bend area will say otherwise.
