I talked to my newly-a-year-older boy today.* We had a delightful visit; he is a fun person and had me laughing for an hour.
He had some startling statistics that had me saying, "So, that explains it!"
If you are dehydrated by just 5% your mental capacity will be diminished by as much as 25%. By the time your body says to you, "Hey, I'm thirsty," you are dehydrated by 10%.
This explains a lot about Utah drivers.