Speeding can kill or seriously maim innocent people. However, if every British motorist who exceeded a speed limit was prosecuted the roads would be empty in no time. Therefore, not everyone who apparently exceeds the speed limit gets prosecuted, even if they are detected by a police car or a camera. There are some circumstances which make prosecution unlikely - but still a real possibility!
Speed camera calibration and the ACPO guidelines
Speed cameras such as Gatsos are calibrated with a margin of error of two per cent, so, usually, no action will be taken at speeds below 102 per cent of the limit.
It is also accepted in some forces that speedometers can often be up to 10% innacurate.
This means that some police officers will ignore speeds up to two miles per hour plus ten per cent of the legal maximum - depending upon whether or not there are other safety factors, such as the vicinity of elderly people or children, bad visibility, slippery road conditions etc, which would make high speeds even more dangerous.
The Association of Chief Police Officers recently revised its guidelines on the enforcement of speed limits. These new guidelines suggest (but do not require - this is a VERY important difference!) that margins for police action are set as follows;
|Speed limit||Action speed||Summons speed|
The 'action speed' is the speed at which either a fixed penalty or a speed awareness course will be considered; the 'summons speed' is the one which, if exceeded, should result in the offender appearing before a court which would have the power to levy a heavier fine, disqualification or even imprisonment.
For a band of up to 10 per cent plus 6 mph (for example, up to 39 mph in a 30 mph limit) immediately above the lower threshold, drivers may be offered the alternative of a speed awareness course if they are eligible. The guidelines make clear that these limits do not remove the police officer's discretion. Drivers are much more likely to be prosecuted if, for example, they are near a school which children are leaving, or if visibility is poor.
The ACPO guidelines also point out that enforcement needs to be consistent, but that if a stretch of road does not 'feel like' a road with a certain limit, the limit will tend to be widely ignored and enforcement may become difficult.
Car speedometer accuracy
Many drivers who use satellite navigation equipment routinely notice that their speed as shown on the satnav is lower than the speedometer reading. This has its roots in a European standard which requires that a speedometer can read up to 10 per cent above true speed, but never below it. To ensure that they comply with the law, therefore, car manufacturers will calibrate their speedometers to read slightly high - sometimes up to the full ten percent allowed by the standard.
Since a speedometer actually measures wheel revolutions, the size of the wheels has an effect on the accuracy of the result. New wheels, or even tyres, can produce a change in the speedometer reading.
Contesting a speeding ticket - making excuses
It is important to remember that speeding is what is known as an 'absolute offence'; this means that unless you can prove that you were not speeding you are guilty, regardless of the circumstances. Factors such as a faulty speedometer or an urgent appointment will only be mitigation.
Who can break the speed limit?
The Road Traffic Regulation Act 1984 gives emergency services - fire, police, ambulance permission to break the speed limit 'if the observance of that provision would be likely to hinder the use of the vehicle for the purpose for which it is being used on that occasion'. However, the court may decide that on a given occasion, that exemption did not apply, and police drivers have sometimes been prosecuted.
Courtesy towards police officers
The officer who pulls you in when you are doing 31mph in a 30mph zone is just doing a job and acting within the law. Please remember that this person may have considerable discretion in whether or not to recommend that you be prosecuted - something that could have severe repercussions for you. No matter how frustrated you feel, a smile and a cheerful greeting will probably do you more good than an aggressive attitude, which could get you into far more trouble than you may already be in! So, act courteously and co-operate with any reasonable requests or instructions, and you may yet get off lightly.