As drug-driving arrests increase, motorists are being urged to check any medication carefully, particularly those that suffer from hay fever, before getting behind the wheel.
The number of motorists charged with drug-driving has increased dramatically over the last 12 months, with prescription medication cases accounting for much of the rise.
In 2015, 1,686 drivers were caught drug-driving, compared with only 738 in 2014 – a rise of approximately 140%.
That's according to new data obtained by Confused.com via a freedom of information (FOI) request.
Of the one in seven drivers who admitted to the offence, the majority were taking prescription medication rather than illegal drugs.
Motorists 4 times more likely to drive on legal drugs
This rise coincides with changes to the law that came into effect in March last year, which saw new road-side drug screening devices introduced.
New drug-driving limits for a wider variety of drugs – both illegal and prescription - were also brought in.
Many of the guilty drivers were under the influence of class A to C drugs, such as cocaine, ecstasy, and cannabis.
However, British motorists are four times more likely to drive under the influence of legal drugs, such as diazepam and codeine, than their contraband counterparts.
1 in 3 drivers suffer from hay fever
Britain’s hay fever sufferers could be at particular risk of inadvertently committing a drug-driving offence.
More than a third of motorists across the country suffer from the pollen-affliction.
And, according to the Royal Pharmaceutical Society, some hay fever medications can have side-effects that could impair your driving ability.
But one in seven drivers who suffer admit to not reading the advice leaflet before they take their medication.
1 in 15 admit their driving has been impaired
Perhaps worryingly, one in 15 motorists who suffer from hay fever admit that their ability to drive has been impaired while under the influence of medication.
And 4% of these motorists have had an accident as a result.
Some of the more common side effects that these motorists have experienced include drowsiness, lethargy and blurred vision.
Matt Lloyd, motoring expert at Confused.com, says: “It’s worrying to see that so many motorists admit to driving while under the influence of drugs – both prescription and illegal.
‘New drug-driving laws having an impact’
“However, it would seem that new drug-driving laws introduced early last year are having an impact, with the number of drug-driving arrests increasing by 144%.
“This means more motorists who are found to have broken the law are being caught, which in turn will help to make our roads a safer place.
Lloyd adds: “Our advice is simple: before taking any medication people should always read the safety leaflet before driving.
“Or if unsure they should ask the pharmacist or err on the side of caution and don’t drive, as road safety for themselves and others should be a top priority for any driver.”