New measures to counter drug-driving have been included in a draft of the new road safety strategy. David Labanyireports on what is a growing problem.
Gardaí and road safety agencies are increasingly turning their attention to drug-driving as international evidence suggests the issue could soon surpass drink-driving as a cause of crashes.
It is a more complex challenge than alcohol as it includes legal medicines, illegal drugs and combinations of both which can seriously impair a person's ability to drive.
Unlike alcohol, current legislation does not set a prohibited concentration for drugs and makes no distinction between legal or illegal drugs. The only criteria for a prosecution is whether a driver is deemed impaired and whether the impairment is caused by one or more drugs.
The extent of the problem is traditionally underestimated in Ireland because the Garda and court services statistics do not distinguish between impairment caused by alcohol or drugs or both and list only convictions for "impaired driving".
Also, unlike alcohol for which all drivers can now be randomly tested, motorists are sent for a drugs test only after being stopped for driving erratically but found to be under the alcohol limit.
Samples from suspected drug-drivers are analysed by the Medical Bureau of Road Safety which tests for seven drug classes: amphetamines, methamphetamines, benzodiazepines, cannabinoids, cocaine, opiates and methadone.
Prof Denis Cusack is head of the bureau and says people must become equally aware of the impact of their drugs as they are of alcohol when driving.
"Some drugs act as sedatives, others as stimulants and others have a psychotic effect. A combination of two or more of these, either legal or illegal, can create a very significant and, often unexpectedly, severe impairment on your ability to drive," says Cusack.
A large number of drugs cause drowsiness and slow reaction times, he says. These include over-the-counter cough mixtures with codeine, older anti-histamines and drugs for anxiety or stress.
"However, the wrong thing for people to do is panic and stop taking their medicine if they need to drive. If you are unsure, talk to your pharmacist."
While most patients can comfortably discuss side effects with their GP or pharmacist, they are less likely to ask how their medicine interacts with a line of cocaine, a cannabis joint or even a glass of wine or beer.
Last December Cusack and other UCD researchers published a study on drug-driving in Ireland based on a sample of 2,000 drivers. This found that a third of drivers arrested for driving erratically but under the alcohol limit had taken drugs, with cannabinoids the most common. More than half the drivers testing positive had two or more drugs in their system.
A further 14 per cent of drivers already over the alcohol limit also tested positive for drugs.
Dr Paul Skett is a senior lecturer in pharmacology at the University of Glasglow's Institute of Biomedical and Life Sciences. He is frequently an expert witness in prosecutions involving drug- driving and says in almost all cases two or more drugs are involved.
"When talking about drug-driving you need to split them into different groups. Amphetamines, ecstasy, speed, cocaine are all stimulants that speed up your thinking processes.
"They heighten confidence and aggression which leads to driving at higher speeds. Drivers on these substances take more risks and, for example, might try to make it through a red light or overtake when perhaps they shouldn't."
He says as with most drugs the more you take the worse the effects. "A line or two of cocaine is quite sufficient to give you that superman effect, making you think you are indestructible."
Cannabinoids produce the opposite effect and tend to relax a driver, making them drive slower.
"However, because their spatial awareness diminishes, the driver tends to follow the white line in the middle of the road. Because they can't judge distances or speeds and just concentrate on tracking the white line, they tend to drive over the white line."
The amount of cannabis required to produce this effect is quite small, a couple of joints would have this effect on the brain, he says.
After cannabis, the second most commonly found drugs in Irish drivers are benzodiazepines. These psychoactive drugs such as Valium, Librium and Xanax are used to treat a variety of conditions including anxiety, stress and panic attacks.
"These are all similar to alcohol as they are depressants and slow the working of the brain," says Skett.
"In low doses benzodiazepines depress inhibition so you get an excitation first. At slightly higher doses the effects start to mirror those from alcohol - the driver becomes lethargic and unco-ordinated and their ability to judge speed and distance declines," he says.
However, benzodiazepines mixed with alcohol is one of the worst possible combinations for impairing drivers, says Skett.
"Both are depressants and when they interact can make you lethal on the roads. Let's say someone has a drink after work. They are legally under the limit but because they are also on Librium the resultant impairment is actually equivalent to having three or four drinks."
Skett is sceptical about the extent to which warnings about the side effects for drivers on medicine information leaflets are used.
"I don't think people take the slightest bit of notice of them to be honest. The warnings are deep in the small print of the patient information for legal reasons. Most make no reference to combinations with other drugs or alcohol."
The UCD drug-driving study found that drivers under 25 years of age were mostly likely to test positive for cannabis, with drivers aged 35-44 showing the highest prevalence of benzodiazepines.
Cocaine and methadone use was most common among 25-34 year-olds. The report found drug-driving was quite age specific. Drivers under 25 were 20 times more likely to test positive for drugs than over-65s.
International evidence suggests that for every two drivers over the alcohol limit there is at least one impaired by drugs and that drug use is on the rise.
In 2003, the European Union warned crashes from drug-driving could soon outstrip those caused by drunken drivers and many European states are introducing specific measures to counter drug-driving.
Sweden and Switzerland have imposed a zero tolerance level for illicit drugs which means any trace of these substances is sufficient for a conviction.
The Road Safety Authority wants to increase drug-driving enforcement by introducing a roadside test of a driver's co-ordination. If the driver fails the test, a blood or urine sample is taken. This test is already being used by some British police forces.
Data from the British Department for Transport suggests that one in five drivers involved in a fatal crash has traces of illegal substances in their system and that overall drug-driving has increased six-fold in the past 20 years.
British police have started a summer campaign to randomly target drivers under the influence of illegal and prescription drugs based on the roadside impairment test.