I suppose it'd be like 20mph zones. Not generally enforced...
That's exactly why I
won't sign it. The current (unenforced) position is that motorists should be well across the white lines on many roads (see Highway Code), which is more like four or five feet. If we were talking about prosecution simply for passing closer than three feet, this proposal might make a difference. However, I can't see that happening, and indeed I'm a bit hesitant about whether that's the kind of general regime that I want.
But it won't happen. The most that is likely is that it would be picked up and put into the Highway Code, thus watering down a provision that is admittedly not as widely known as it should be, but stronger than the proposal.
So, as I see it, this campaign is going to give us a new (unenforced) position of three feet - which is trading two feet of clearance for a bit of publicity. After that fades, what do we do? Trade another two feet for some more?