Coffee Helps Travelers Stay Alert

Caffeine from one cup of coffee is enough to sharpen awareness so people drive safer

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Driving can be a real drag, but many people keep their mind focused with a hot cup of java. A recent study defends this intuitive decision by savvy travelers.

One cup of coffee has more than enough caffeine to sharpen awareness, and more aware drivers are safer drivers. After just one cup of caffeinated coffee, test subjects demonstrated better results on driving simulations, including less lane drifting and more consistent speed maintenance.

"Drink coffee on long commutes for a safer driving experience."

The author of this study, Monique Mets, Ph.D., has been documenting the effects of caffeine on driver safety for several years. Working out of the Utrecht University in the Netherlands, Mets and her team have sought to prove what most people already intuitively knew about coffee and driving.

Previous studies have shown that caffeine helps travelers drive more safely, but those studies examined the effects of four or more cups of coffee on drowsy drivers. This is the first study of this kind that examines the effects of low doses of caffeine on the driving ability of well-rested people.

The study included 24 test subjects, 12 men and 12 women, who were screened for alcohol or drugs as well as sleeping habits. Only subjects who were deemed well-rested and not using drugs were allowed to participate in the trial. Participants were instructed to abstain from both caffeinated beverages and alcohol for a period of 24 hours prior to their driving simulation.

Mets and her team subjected the research participants to a driving simulation. After two hours of simulated driving, subjects were given either decaffeinated coffee or regular coffee (which contained a measured dose of 80mg of caffeine) and continued the simulation for an additional two hours.

Driving safety was objectively measured based on whether the subjects could maintain a constant speed while staying in their lane, though they were allowed to overtake slower “drivers” in the simulation.

There were also subjective measures, such as how well the subjects rated their own driving, how much mental effort each subject put into the simulation and how the sleepy the subjects felt.

For the first two hours, both groups performed at essentially the same level. During the second stage of the simulation, however, distinct differences were seen in both the lane position and speed maintenance of the test subjects.

In another study conducted by Mets, she examined the effects of legal-limit intoxication of alcohol on the same driving simulation. The difference between sober and non-sober was similar to the difference between caffeinated and non-caffeinated in this present study.

In other words, the people without caffeine had significantly less safe driving results. The decaffeinated subjects were not able to stay in their lanes nor maintain a constant speed to the level of their caffeinated brethren.

In the subjective measurements, caffeinated subjects reported less mental stress in performing the simulation, as well as rating their own performance higher than their decaffeinated counter-parts. Not surprisingly, caffeine also helped stave off the black dog of drowsiness that can be so dangerous when driving long distances.

There are limitations inherent with simulated driving as compared to real life driving experience, but these results reinforce what for most people is complete common sense. Caffeine makes drivers more alert.

This study was completed in the summer of 2011, and is published in the February 8 issue of Psychopharmacology. There were no reported conflicts of interest.

Reviewed by: 
Review Date: 
March 7, 2012
Last Updated:
March 10, 2012