Idea Man,

Sounds just about perfect. Police won't suggest trying to direct traffic in a busy intersection unless you've been trained. It can make a bad situation worse. You might have stayed with him, but most people will go out of their way to not hit someone, so as long it's not a highway, he's likely going to be okay every time.

Gauge

(side note: when people are dehydrated, one of the signs is belligerence.
this is compounded with a brain injury.

So, it is helpful to give water to such people

every twenty minutes and copius restroom breaks