The government are to set limits for drug driving, similar to those we have for drink driving, in the Autumn of 2014.

A zero limit was ruled out because it was felt that people could have been accidentally exposed to drugs such as passive smoking of cannabis, which may result in a small trace in their bloodstream but wouldn’t impair their driving.

It is expected that when the new law comes into force there will be different limits for different types of drugs.  Not all these drugs will be illegal – some will be legally prescribed drugs such as morphine and diazepam.

It will mean that is it easier to prosecute people for drug driving because anyone over the limit can be prosecuted, whereas now, the police need to prove that your driving was impaired, which can be more difficult to prove in court.

But what is the safe limit?

As with drink driving, the difficulty is that we all know what a pint of lager looks like, but we don’t know what 35 microgrammes per 100 millilitres of breath looks like. Alcoholic drinks are all different strengths and no two people process alcohol the same, which adds to the uncertainty. With the drug driving limits, not only will we not know what 2 micrograms of cannabis per litre of blood looks like, but these limits will vary from drug to drug and then there is the uncertainty of how long it will affect each individual.

With alcohol and drugs, the only safe limit is a zero limit.  If you are on prescribed drugs that may affect your ability to drive, then you must seek medical advice.