It's interesting that before this, legal impositions down the years were primarily to do with safety - seat belts, where children sit, mobile phones etc. Isn't the smoking ban the first on health terms rather than road safety (inside the cabin rather than engines etc)? I wonder whether this changes the definition of private space?
Oh and to join in with the when I was...Both parents smoked, surviving one still does and had four kids in car.
Then again, quite often on school runs or birthday parties you would have one kid in the front, four to five in the back seats and two to four kids in the boot of the Cortina estate flicking V-signs at oncoming drivers 