Intoxicated friend?

Despite the fact that I felt like I was baking in the sun for an hour and couldn't see most of the crash scene, it was still a good presentation. A point that was made was that many people end up in drunk driving crashes because they wont refuse to get in the car with their intoxicated friend or parent. I wouldn't get in the car with a friend, but who really says no to their parent? It's a difficult choice to make. What would you do?