Friends Don't Let Friends Drive Thirsty

I'm pretty sure that you're supposed to hydrate with just plain water -- about 7 ounces per hour of driving, according to the results of this experiment. The good news is that's not enough to make you pull over for a rest stop every 30 minutes.

UK Telegraph

"In the study, published in the journal Physiology and Behavior, the researchers carried out a range of tests over two days on male drivers using a laboratory-based driving simulator.

Each volunteer visited the laboratory on three separate occasions and used the simulator on one day while normally hydrated and on a dry day.

The simulated driving task included a two hour continuous monotonous drive on a dual carriageway, with bends, a hard shoulder and simulated auditory ‘rumble strips’, and slow moving vehicles which had to be overtaken.

On one day, the men were provided with 200ml of fluid every hour, and on the dehydration test day, only 25 ml an hour.

Drivers errors, including lane drifting, late braking, and touching or crossing the rumble strip or lane line, were calculated for each condition and compared.

Results show that there was a big increase in driving errors.

During the normal hydration test there were 47 driving incidents, but when the men were dehydrated, the number rose to 101.

The error rate also increased during the two hour period, peaking in the last quarter.

"The results of this initial exploratory study suggest that mild dehydration resulted in a significant increase in minor driving errors during a prolonged, monotonous drive, compared to that seen while performing the same task in a hydrated condition," according to the researchers."