I was riding my bike late at night when I saw a car going slow and weaving across the road, coming within a foot of hitting me. I suspected that the driver was drunk. We both stopped at the next red light and I knocked on the window. I could tell she was seriously intoxicated and I said that I was going to call the police with her license plate number. She then sobbed and begged me not to do so and even asked if I could drive her car home. She seemed scared and thought that driving home drunk was the only way for her to get home.
So I decided to do a good deed. I asked her to immediately stop the car and put the hazards on and give me the keys. I drove the car into the parking lot of the gas station right next to us, just to get it off the road. Then asked her to call her parents and say that she was driving drunk and ask for them to pick her up, all the while holding her car keys so she could not drive. I figured that her parents would get mad at her and that would scare her into never driving drunk, without the lifelong consequences of a DUI. Gave her the ultimatum "it's either your parents or the police".
I waited 20 minutes for her mom to show up, and she immediately hugged me, thankful that I was concerned for her daughter's safety. Of course, she was mad at her daughter as I had expected, and I hope she punished her.
I feel like I did a good deed, effectively getting a young drunk driver off the road. She got lucky that she had to deal with me, rather than getting pulled over, or worse, causing an accident.