>They wouldn't do it on a regular section of motorway with a 70 limit, why do it in a 50? I would guess because 70mph is the default speed on a motorway, and t

>They wouldn't do it on a regular section of motorway with a 70 limit, why do it in a 50? I would guess because 70mph is the default speed on a motorway, and the highest speed limit possible, and it's generally accepted that people often drive faster than that on motorways in the UK. Whereas 50mph is unusual and thus seems more intentional, and thus more likely to be enforced.