How do drugs affect driving?

Whether prescription, over the counter or illegal drugs, they can impair driving skills including vision, reaction time, judgment, hearing, and simultaneous task processing/accomplishments. Driving requires other cognitive skills such as information processing and psychomotor skills, which may also be impaired by the use of drugs. When drugs are mixed with alcohol, the results can be devastating.

Alcohol alters the mind, affects thinking, judgment, slows reaction time and interferes with coordination. Tasks requiring divided attention are most sensitive to alcohol effects. The more a person drinks the more likely that person is to drive. Alcohol and other drug involvement are much more likely in nighttime crashes.

Marijuana is also mind altering. Thinking and reflexes are slowed, causing difficulty in responding to sudden unexpected events. A driver’s ability to “track” or stay in his lane, to brake quickly, and to maintain the correct distance between cars is affected.

Cocaine is a brain stimulant that causes anxiety, delusions, seizures, and lack of concentration, memory problems and blackouts. There is an increase in impulsive behavior with tendencies to take more risks and create confusion within the user. A person using cocaine maintains the illusions of being alert and stimulated although physical reactions are impaired. The most dramatic effects of cocaine and driving are on vision. Cocaine may cause higher sensitively to light, halos around bright objects, and difficulty focusing.

Tranquilizers and Barbiturates are particularly dangerous in conjunction with alcohol because the mixture increases the accident risk beyond that found with anyone on drugs alone. Particularly strong is the interaction between alcohol and diazepam (Valium).

Over the counter medications Alcohol can enhance some of the dangerous side effects of the medications so to make driving dangerous. Most drugs for colds, hay fever, allergy, or to calm nerves can make a person drowsy when alcohol is consumed.

With stimulant-based drugs, a driver would actually feel that they were a better driver while they were under its influence, but they would become much more likely to drive recklessly and dangerously.
With depressant-based drugs, the driver would lose any real anxiety about the dangers on the road and would not be able to react quickly to changing driving conditions.
With hallucinogenic drugs reaction time will be altered and the driver’s ability to operate the vehicle will become erratic.