In Australia, we have random breath testing. Some of these involve huge police roadblocks that stop entire freeways, testing thousands of people in a night. Up until the age of 22 in most states a blood alcohol level of 0.00 is enforced and after that it is 0.05. This allows us to have a drink or two when we go out; any more than that and you are risking you're licence. Needless to say, not many people drink and drive; particularly in my generation.
I noticed this a lot when I was in Australia. People just flat out don't drink and drive, although we did drink in the backseat while driving on some road trips in the country. .08 -> .05 makes a huge difference in what people believe they can get away with. I don't ever drink and drive because the times I have done the breathalyzer machine at the bar, or with a group of friends that has one, I am always over even if I am physically feeling 100%. Sucks being tiny.
Yeah they're pretty bad in LA. It's a complete bitch to sit through them. If my boyfriend and I ever go anywhere on a weekend/holiday I check facebook first. Usually if theres a checkpoint in the area it'll be on the top of my feed and we avoid that route. The worst is they sit cops at the last place to turn before the checkpoint so you have to completely avoid the area. Driving down x street and turning right a block before the checkpoint is a guarantee pull over by the sneaky little fuck waiting for the people avoiding the lineup.