How Police Detect Drink and Drug Drivers

Motorists who believe they can drink or drug drive with no consequences are likely to be in for a nasty shock. Not only do they risk their own lives and those of others by doing so they are, contrary to popular belief, quite likely to be found out by the police.

West Mercia Police averages around five arrests per day for drink or drug driving offences, thanks to day-to-day targeting and specific enforcement operations. Every time the police attend a road traffic incident, they breathalyse the drivers at the scene.

In 2008, police administered 14,000 breath tests in the West Mercia area, of which 1,600 were either positive or the driver failed or refused to provide one.

Police officers also receive detailed training to recognise the signs of drug use in drivers. They use what is known as field impairment tests, which is based on an observation of impairment, rather than a biological test.

Five field impairment tests are used in the UK and these are easy to carry out if you are not affected by any substance, but they become much more difficult if you are:

• Examination of the driver's eye pupil size and condition.
• The Romberg test - assesses balance and judgement of time. The subject is asked to tilt their head back, close their eyes and estimate the passage of thirty seconds.
• The walk and turn test - the subject must walk heel to toe along a straight line, counting their steps out loud and looking at their feet while doing so.
• The one leg stand test - the subject must stand on one leg while counting out loud.
  
• The finger to nose test - with the head tilted slightly backwards and eyes closed, the subject must touch the tip of their nose with the tip of their finger with the hand indicated by the officer.