Select Committee on Home Affairs Memoranda


Drug Driving

  1.  The law currently prohibits driving "whilst unfit through drink or drugs". The current law does not require major modifications to be effective. However, there may be a case for secondary legislation to be amended to provide more effective enforcement.

  2.  To secure a conviction, the police/Crown must prove that:

    (a)  The driver was under the influence of drugs,

    (b)  His ability to drive properly was for the time being impaired,

    (c)  That the impairment was due to drugs rather than other factors (eg disability, illness, fatigue etc).

  3.  IDMU has been consulted by the Transport Research Laboratory and Northamptonshire Police in developing more effective methods of enforcement for the existing laws.

  4.  The "field impairment testing" (FIT) currently being adopted by many police forces, represents an improvement on previous enforcement techniques, but fails to address abilities which are directly related to the ability to drive, in particular reaction time and tracking ability. These could be addressed via development of an in-car simulator to allow suspects to be tested at the time, with objective pass/fail standards. We have also recommended that all FIT tests are recorded on videotape where such facilities exist within a police vehicle, as too much of the present test is subjective on the part of the police officer involved.

  5.  The taking of samples of blood for drugs provides a snapshot at the time the sample is taken, which may represent a baseline level or the residue of a higher dose influencing the driver at the time (particularly for cases involving cannabis). We recommend that legislation be amended to require the taking of at least two samples a fixed time (eg 15 minutes) apart to determine whether a drug level is stable or declining, and to enable back-calculation to the time of the incident in question.

  6.  Despite much public alarm, the effect of most controlled drugs on driving provides less of a risk of accidents than alcohol or prescribed benzodiazepine drugs:

    (a)  Cannabis—Increased risk for new users or new drivers, for established users/drivers appears to reduce accident risk by improving driver behaviour (slower speeds, larger gap, fewer risky manoeuvres) compensating for any performance impairment (tracking ability may be affected, no effect on reaction time),

    (b)  Stimulants—Low doses of amphetamine or cocaine may improve performance (alertness, quicker reaction times), although high doses impair judgement (overconfidence, aggressiveness),

    (c)  Opiates—Impair naive users, addicts probably drive better with drug in system than when withdrawing,

    (d)  Ecstasy—Our surveys suggest significantly increased risk of accidents, but may be confounded by social factors (eg fatigue due to driving in the small hours of the morning when returning from clubs/raves),

    (e)  Hallucinogens—severe impairment of perception and judgement—few users would contemplate driving under the influence.

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Prepared 20 December 2001