Brian,
Unless he wants to stop he will not. My advice is to see if he feels it is a problem. If he feels it is not but you think that he is blind to his problem – you can risk your friendship and point out 3 or 4 things you see as a problem. If he is not an alcoholic he may straigten up right away. If he is an alcoholic this conversation may save his life (or those he could kill on a highway).
If he wants help there are many resources that I could point to.
