In preparing my "Why The Wire is the greatest thing since sliced bread" column for this Sunday's paper, I listened to a few of the commentaries on the season three DVD set (it comes out on Tuesday). During one of those famous McNulty and Bunk drinking on the train tracks scenes, David Simon marvels that not a single critic has bothered to analyze the symbolism behind that recurring visual motif, and challenged anyone listening to give it a shot before season four begins.
So dared, I gave it a lot of thought, but the best I've come up with is the idea of Jimmy constantly getting in front of oncoming trains (i.e., the Burrell and Rawls administration). He may think he's strong or smart enough to stop them, but the train's just gonna keep on coming.
But that's just my theory. I figure I'd open it up to the room; if your theory makes its way into a column, I'll be sure to credit you, and I'll definitely send Simon a link to all the responses.