BAKERSFIELD, Calif. -- Researchers had 67 people with mild to moderate Parkinson's and 51 healthy people about the same age go through a driving simulation -- first under good conditions, then in foggy, low visibility conditions, where they were faced with an intersection where another vehicle posed a crash risk.

They found that 76 percent of those with Parkinson's were unable to avoid the crash when driving in simulated foggy conditions.

Researchers noted that those with Parkinson's had slower reaction times, and they tended to be driving an average of 10 miles per hour faster at the time of the crash than those who did not have Parkinson's.

Though Parkinson's most notably affects movement, visual skills, such as the ability to see contrast and to process visual information quickly are also compromised.