What lengths would you do to assure someone does not get on the roadway drunk?

What would you do if you were out for a night of fun and one of the persons you know got sloppy drunk and they refuse to take a cab even if they did not have to pay for it? They won’t surrender their keys or accept a ride home because they feel the area is not that safe and their car will get stolen, broken into, or left on blocks (wheels and tires ripped off) if they left it there over night. They truly believe they could drive home since they live about 4 miles and change away. To make sure their car does not enter the roadway with them behind the wheel what would you be willing or prepared to do?