The legal speed limit that is aloud is actually 10% over the speed limit so motorway travelling is 77. So someone travel in a non mb car at there speedo reading of 70 is actually travelling at 64ish and someone travel with sat nav speed (gps) 100% accurate of 77 is actually travelling 13mph faster which is a hell of a lot of difference. Imo 75% maybe more of people that overtake you on the motorway have gps speedo.
I say non mb cars because every mb I have driven with sat nav speedo reading has been almost perfect, oh apart from my police vito that was calibrated at new and that is 2 mph slower at 70
The legal speed limit is 70 mph. To comply with Construction and Use regulations, your car speedo may over-read by up to 10%, but may not under-read. The ACPO guidelines - which not all forces use, but most do - recommend that no enforcement action be taken if your speed is no more than 10%, +2 mph, over the speed limit. Hence, in a 30 mph limit you will PROBABLY get away with 35 mph; 40 limit, 46 mph; 50 limit, 57 mph; 60 limit, 68 mph; 70 limit, 79 mph. Those figures apply to speed camera settings, because cameras have no brains or discretion, and do not discriminate between soaking wet, crowded motorways in the rush hour and bone-dry deserted motorways at three o'clock in the morning.
HOWEVER.... The police live in (and police) the real world, and provided you are doing nothing illegal, stupid or foolish in addition to speeding, you may well get away with rather higher speeds. The police are there to keep order, not hand out pointless speeding tickets for a few mph over the limit. A traffic police friend of mine once told me that on the motorway, unless you are committing another offence you will probably be OK up to 85 mph, MAY be pulled over up to 94 mph, and WILL be pulled over at speeds higher than that.
If you do get pulled over, the police still have considerable discretion. Generally speaking, policemen are not looking for trouble, they're looking for a quiet shift with no paperwork to keep them on after they should have finished, and they have a sense of humour (mostly...). If you were doing 120 mph, don't expect that saying "I don't suppose this will help" and handing the officer a Get Out Of Jail Free card from a Monopoly set will get you off ( it just might, though).
If you're asked "Do you know why I stopped you?", there is no right answer, but "F**k knows; nothing better to do?" or "Why aren't you catching real criminals?" are definitely wrong answers. A(nother) friend of mine was stopped on a bike at over twice the legal limit, riding a bike capable of a whole lot more, and asked "Do you know what speed you were travelling at?". He replied "Not exactly, no, but when I'm going that fast, I prefer to keep my eyes on the road". The copper, who was also a biker, laughed, and he got away with a friendly lecture.
Be polite and reasonable, and you are likely to get politeness and reasonableness in return.
There is no specific "target" for any quota, he just gets an "interview with coffee" should he not have enough "collars" over a period of time.
