Facts: My friend just gone done for 48 in a 40. They told him the law in that county was 10% + 3 which would have come to 47. Off to a speeding course he goes.

Facts: My friend just gone done for 48 in a 40. They told him the law in that county was 10% + 3 which would have come to 47. Off to a speeding course he goes. Made up: I thought the 10% came from the rules the speedometer is calibrated against which are +10% -0% i.e. Your speed will be 30mph but you could be doing 27. You will never be doing 31. I guess the plus number is whatever the council have chosen to enforce. Another person from the country thinks it's 10%+2 edit: Here you go, it's a more nuanced than above. Europe's law. Read Page 8 - http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/... Displayed (V1 ) and the true speed (V2) 0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h