Motorists who tailgate other motorists in the UK are to be referred to as 'shaggers' because they physically drive too close to the vehicle in front and invade their private space. In principle they are letting their bonnet enter the private space of the rear of the vehicle in front since every vehicle has a private space around it.
So in future if you have a vehicle being driven too close to you from behind and invading your rear private space then this driver is a shagger because he is shagging you.
Unfortunately, there are too many shaggers driving all sorts of vehicles on the roads today. Shagging a vehicle in front will eventually become a criminal offence and called 'Mobile Rape' since it has been conducted without consent of the driver of the vehicle in front.
Some motorists would prefer to call it 'bumming'.