The new legislation takes effect from 2 March 2015 in England and Wales and sets limits at very low levels for eight drugs commonly associated with illegal use such as cannabis and cocaine.

There are also eight prescription drugs that are included within the new law. These are:

• Cloanzepam
• Diazepam
• Flunitrazepam
• Lorazepam
• Oxazepam
• Temazepam
• Methadone
• Morphine

However, the limits that have been set for these drugs exceed normal prescribed doses, meaning that the vast majority of people can drive as they normally would, so long as they are taking their medicine in accordance with the advice of a healthcare professional and/or as printed in the accompanying leaflet and their driving is not impaired.

Robert Goodwill, Road Safety Minister, said: ‘If you are taking your medicine as directed and your driving is not impaired, then you are not breaking the law and there is no need to worry. We advise anyone who is unsure about the effects of their medication or how the new legislation may affect them, to seek the advice of their doctor or pharmacist.’

There will also be a medical defence if a driver has been taking medication as directed and is found to be over the limit, but not impaired.

Drivers who are taking prescribed medication at high doses are being asked to carry evidence with them, such as prescriptions slips, when driving in order to minimise any inconvenience should they be asked to take a test by the police.

Professor David Taylor, Royal Pharmaceutical Society spokesperson and member of the Department for Transport advisory panel on drug driving, said: ‘Don’t stop taking your medicines, prescribed or otherwise, if you are worried about this new law. Instead, talk to your doctor or pharmacist for information about how your medicines might affect your ability to drive. They’ll be happy to give you the advice you need to stay safe.’