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Drugs and traffic

Published 12 December 2005.

In Finland the number of drivers who drive under the influence of drugs has increased considerably during the past 10 years. In 1987, forty drivers were found to be under the influence of drugs (=5,2% of suspects). In 1992 there were 318 cases (=28,5% out of 1117 suspects) and in 1997 as many as 622 (=50,1% out of 1241 suspects). In 1997 the drugs most commonly used by theses drivers were amphetamine (453 cases) and cannabis (390 cases).

Drugs have many effects that increase the risk of accidents. Cannabis products impair your motor co-ordination and your ability to estimate distance, speed and time. Compared to sober drivers, the risk of traffic accidents is 3–5 times greater for drivers who use cannabis. Even moderate doses of cannabis weaken your ability to drive: a regular dose (20 mg of tetra-hydrocannabinol) has the equivalent effect of a blood alcohol content of 0.1% for an occasional user of cannabis. 

Amphetamine and its derivatives make you more willing to take risks, they increase aggressive and impulsive behaviour, and may lead to psychotic reactions. Hallucinations, feeling of omnipotence, obsessions, panic reactions and a lack of control of impulses caused by hallucinogenic drugs will also easily lead to accidents. With LSD and other hallucinogenic drugs there is also the possibility of “flashbacks” which may occur even 6 months after using the drug and after the substance has already left the system. These flashbacks, which involve visual disturbances and problems with estimating time, movement and speed, pose a risk for traffic safety. Withdrawal symptoms increase the risk of traffic accidents especially for opiate addicts.

Occasional use of drugs is as such not an obstacle for getting a driving license, but driving under the influence of drugs is illegal. A person can be persecuted for driving under the influence of drugs when it can be shown that his ability to drive a motor vehicle was impaired. Finding evidence of drug use in the urine sample is not enough. Drugs may show up in tests several days after their effect has ceased. Whether a driver is under the influence of drugs or not is usually assessed by a clinical test at the doctor’s or on the basis of the information that the police has gathered on the incident.

The EU directive on driving licenses came into force in Finland in 1996. It states that a person who is addicted to intoxicants and cannot refrain from driving under the influence must not be issued a driving license, nor must a driving license of such a person be renewed. A person who has been caught driving under the influence of drugs may be monitored for a period of time, during which he will be tested to see if he is still using drugs. His driving license will be renewed only after a doctor, on the basis of regular check-ups, has given a statement that the person has not used drugs for a given period of time.

Different kinds of instant drug tests are being developed that could be used by the police on the road. For the time being the test are only used experimentally.

Timo Seppälä
Doctor of Medicine,
National Public Health Institute