(CBS) It's no secret, driving drunk can be extremely dangerous for the person behind the wheel and anyone else in the car or on the road. A new study suggests another activity while driving might be just as dangerous:
Driving with a cold.
British insurance company Young Marmalade gave computerized tests to drivers who were having cold symptoms, and found cold sufferers had slower reaction times, braked more suddenly and frequently, were less aware of surrounding traffic, and drove more erratically than healthy drivers. The study estimated more than a 50 percent drop in driving ability - the equivalent of drinking four double whiskeys, according to Young Marmalade.
Researchers at the "Common Cold Unit" of Cardiff University in Wales confirmed the insurer's findings in a a separate study, which also found that less-alert drivers are a third more likely to crash into the roadside curb.
One British police chief went so far as to threaten prosecution for sick drivers.
What's so dangerous about driving under the influence of a nasty cold?
Being sick could have a negative impact on a person's mood, concentration, and judgment, according to Young Marmalade. Sneezing and coughing can not only cause shaking, but cause a person's eyes to squeeze shut involuntarily, or to water, which could affect a driver's ability to focus on the road, registered nurse blogger Denise Amrich, wrote on ZDNet.
Dr. Thomas Campel, a physician at Allegheny General Hospital emergency department in Pittsburgh, told CBS Pittsburgh the medications people take to treat cold and flu could also have a detrimental effect on drivers.
Many over-the-counter cold medications "have diphenhydramine or Benadryl in them, which makes you a little sleepy," Campel said. "And then sleeplessness, if someone had a bad night sleep because they were up coughing, or had their cold, they're certainly not as aware and awake as they would be normally."
The bottom line? If you're feeling sick, it might be a wise idea to stay home, or ask a friend to drive you.
"Those with illness with high fever should be staying home for a lot of reasons, including getting needed rest and protecting others from illness," Dr. Christopher Ohl, associate professor of medicine at Wake Forest University School of Medicine, told ABC News. "Perhaps we should add safe driving to that list."