We’re talking about water, folks! We all deplore drunk driving but we usually don’t think about other things that equally affect our driving ability such as hydration. Even a mild level of dehydration can cause errors similar to those made by people who are over the legal drink/drive limit.
A study done with a laboratory driving simulator on people with mild dehydration produced lane drifting, late braking, and crossing over lane lines – many of the errors made by drunk drivers. Dehydration can occur when water loss exceeds water intake and can be fatal if taken to the extreme. Most of us can tolerate a 3– 4% level of dehydration but 5 – 8% causes fatigue and dizziness, 10% causes physical and mental deterioration. As age increases, so does the percentage of driver error with dehydration.
Summer time increases our need for water. So…summertime driving requires good hydration. Often when people drive for distances they minimize their fluid intake due to the inconvenience of stopping to use the restroom. This study actually suggests inconvenience is preferable over dehydration.
How much should we drink? The simplest rule of thumb is half your weight in ounces. A person weighing 120lbs should drink 60oz. The next question 
is usually: what counts? Water is the best choice. Increasing your fruit and vegetable intake also helps since they contain water. Since coffee, tea and sodas contain water so they also count as fluid consumed. Remember that caffeinated beverages can lead to dehydration as well. Water will always be the preferred fluid.
The moral of this story is: drink while driving but make it water. Those restroom stops may be a nuisance but you arrive safely albeit a few minutes later!
