We know that drinking alcohol can impact your driving capabilities, but now a British study says not drinking enough (nonalcoholic) fluids may be just as detrimental.

In a study published earlier this month in Physiology & Behavior, British researchers studied the impact mild dehydration has on a person's driving skills. Eleven men were asked to complete a simulated prolonged drive on a monotonous highway. They performed the task twice: once while properly hydrated and once while not. Researchers studied their driving behavior, taking note of lane changes, lane drifting, and late braking.

The results: If you're dehydrated, you might be a bad driver. People who have a 2% reduction in body fluid status can experience significant cognitive function impairment. In other words, when the men were not properly hydrated, their reaction times were greatly impacted, and the number of driving errors went up compared to the drive when the men were properly hydrated.

A 2% decrease in fluid levels because of dehydration isn't hard to reach. Even as little as 1% can be bad for you. "You're 1% dehydrated, and your mood can flip. We can get cranky. We can get tired," says Kate Geagan, RD, author of Go Green Get Lean. "At 2% dehydration, your problem solving and short-term thinking become compromised. And at 3%, your muscle strength, power, and endurance are decreased."

Whether you're hitting the road for a long road trip or just a quick jaunt up the highway to visit with friends, be sure you (and your car) are properly fueled. Keep a spill-proof water bottle handy, and refill at rest stops. We like Tervis' Water Bottle, which has a 20-ounce capacity and close-tight lid. Its base is small enough to fit most cup holders, too ($27, Another great option: Camelbak's 25-ounce eddy water bottle ($15, Again, it fits comfortably into most cup holders, and its flip-up drinking straw is easy to operate with one hand. Also, it's available in a rainbow of colors.

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