Thinking while driving

You know how they ban talking on mobile phones while driving because
it's distracting? Well what about thinking while driving. Time to
myself is pretty rare around here and although I'm often in the car
with the kids, it's not the same as being with them and entertaining
them - IYKWIM. So a lot of the time that I'm in the car I'm thinking
about this or that - most often thinking up new designs or new schemes
to take over the world. And then I realise that I'm driving on
autopilot or not really concentrating. I scare myself!