Are you driving a car while you have a bad cold? Maybe a bout of flu? You might as well be driving drunk, according to a new study conducted by Young Marmalade, a UK-based car insurance company, and Cardiff University in Wales.

Motor safety experts found that the driving skills of people who were sick were estimated to drop by about 50 percent when compared with those who were healthy. They were more likely to have reduced reaction time and experience a major loss of concentration, so much so that the researchers compared people who were driving under the weather to people who were driving under the influence of "four double whiskeys."

"This small-scale trial provides a warning for motorists," Nigel Lacy, director of marketing for Young Marmalade, said in a statement. " A heavy cold can impair a driver's mood, concentration and judgment."

Young Marmalade did not provide the full study despite an ABC News request, nor did Cardiff University, so the full details on the research remain undisclosed. And because of the lack of details, experts noted that it is difficult to discuss the findings in their entirety.

"As a physician with a master's degree in epidemiology, I wonder about the impact of problems," said Dr. Martin Bittner, staff physician in the department of infectious disease at the VA Hospital in Omaha, Neb. "Are we dealing with something that occurs commonly?  Or is it rare?  Those questions, the [release] points out, lack answers."

While there are no official figures on accidents related to sneezing and other cold and flu symptoms, there are about 500 million colds per year in the U.S, according to a telephone survey conducted between 2000 and 2001. Since about 90 percent of Americans drive every day, about 1 million Americans will be driving with a cold on any give day, ABC News medical researchers tallied.

Researchers at the Cardiff University Common Cold Unit said they simulated driving among study participants by using a black telematics box to record drivers' speed braking and cornering.

It really shouldn't be surprising that illness would decrease alertness and reaction times, said Dr. Christopher Ohl, associate professor of medicine at Wake Forest University School of Medicine.

"Everyone knows that when they have a fever and flu symptoms they are not at their best physically or mentally," said Ohl.  "Those with illness with high fever should be staying home for a lot of reasons, including getting needed rest and protecting others from illness. Perhaps we should add safe driving to that list. One needs to understand there is a wide range of mental impairment from illness, and more minor ailments are really not much of a problem if symptoms are controlled with non-narcotic medications."

But, even in saying that, Ohl noted, "the vast majority of persons with colds or flu are unlikely to be as impaired as that from alcohol or narcotic consumption."