How do you tell if they are drunk if they don't show they're drunk enough to stop serving them alcoholic beverages?
If *I* can tell when a person is drunk then any bartenders should too, it's their job, if they can not tell if their customers had enough, then they shouldn't be in that kind of businesss because it's their responsibility to make sure they serve the limiting of their alcohol to their customers to prevent over-intoxication and even life threatening too..
There are signs that tells you when someone is drunk or had enough ---strong odor of alcohol, vomiting, passing out, aggressive behavior, screaming and yelling, trouble making eye contact, having difficulty maintaining balance and walking independently, unconsciousness, trouble breathing, starting a fight, damaging the property and etc....
And if you see a friend who repeatedly drinking to the point where they are unable to care for themselves or are acting aggressively then you know your friend is unable to drive...
I don't know if it's bartender's job to look after people's drinking problems or they end up going to drink and drive. They don't have time for that because they have to focus on serving thousands of people in one night. Unless they're staffed enough to serve a night of partying. Maybe, they should hire people who are responsible for checking on people's drinking problems or making sure they don't go out and drink and drive. That would work in a very busy club/bar that have so many people to check out. Smaller bars would have bartenders to check them out because there's less people.
If that's a problem then they should hire a bouncer or security/police personnel for assistance....