As tough as it is, you MUST talk some sense to him. Take him out for a lunch/dinner, when both parties are sober and let him know how you, your friends and everyone around him feel about the situation. Tell him he is going down the wrong path, and if he won't do anything about it, you certainly will. If he is hiding his problem from his folks/family, well then he is scared what they would think or do about the situation.
That being said, try rationalizing with him first, then let him know the exact course of action you plan on taking if you see no change. It's sad how some people can't control themselves. Trust me, I am no angel, but a good friend of mine had problems with cocaine. It was seriously out of control, and I was a big part of it, but still had the balls to tell him he had a problem, night in and night out while we were both partying.
It finally came to the point where I said, listen, this **** has to end, I am here for you. Let's do it together, we'll find someone you can talk to but you have to want to do it. I gave him a 2 day deadline to come to me first and seek help. He didn't come around, so against my will I went to his older brother and folks. I really had no choice, this is one of my best friends and I couldn't see this **** anymore. He, like your friend, also has 3 DWI's and I went ahead and sat his gfols/bro down. After I was done, part of me felt like **** for "betraying" a friend, but the other half felt great in knowing that now someone else will do something about it, someone that he previously feared.
That being said, he got an ass whipping from his brother, sense talked into him by his mother and went to rehab. 10 months later now, he is not completely clean, but the change is remarkable.
All it takes is to put a little pressure on that person himself. They will fight and deny until something bad happens. You can't let that happen. General, please help your friend, and the innocent bystander that is waiting to be killed. Drinking and driving is one thing, but if you can't keep your eyes open, then it's a problem. Do something for your friend before it's too late.
Keep us updated as I am hoping to hear a success story. I have tons of info on this **** if you want to send me an email. Psychology type **** which may be able to help. Talk sense into him!
GL
Treez