Just to expand a little on heathfield�s post, the Association of Chief Police Officers has issued guidelines for the prosecution of speeding. They are in two parts: one table shows the speed required to be registered before a fixed penalty is applied and this is the �10% + 2mph� formula which heathfield has quoted. This level is set to avoid unnecessary arguments over speedometer calibration, measuring device calibration and so on. The table for each of the speed limits is:
20mph � 24
30mph � 35
40mph � 46
50mph � 57
60mph � 68
70mph � 79
Below this speed and no action is normally taken.
The ACPO have also issued a second table and drivers exceeding these limits are not normally offered a fixed penalty, but are summonsed to court instead. Magistrates hear the case and would normally impose a stiffer penalty. The table below shows the maximum speed allowed before a summons is issued:
20mph � 35
30mph � 50
40mph � 66
50mph � 76
60mph � 86
70mph - 96
The maximum penalty for speeding is a fine of �1,000 (�2,500 if on a motorway) and the imposition of up to 6 penalty points OR a ban. (Magistrates have the power to impose a lifetime ban for any endorseable driving offence, but rarely go beyond 5 years even for the most serious). Their normal guidelines cover speeding offences where up to 110mph (in a 70 limit) is recorded and for this they are recommended to impose a fine of one week�s net income, plus either 6 penalty points or a ban of up to 56 days. It is open to their discretion to impose stiffer penalties for speeds beyond this.