Having to urinate really bad while driving is equivalent in terms of impairment to about a 0.05 blood alcohol level, according to research done by Dr. Peter Snyder, a VP of research at Rhode Island Hospital. “With urination, it’s a very active process, as you know. It takes lots of concentration,” Snyder tells Jalopnik. “If you’re on the highway at 70 mph, and you really have to go, you really are impaired. You can’t let it get to that point.” So don’t let friends drive with full bladders.