Depends on what you mean by "crowded". If you mean "bumper to bumper", no. But in conditions which are slightly less heavy, traffic tends to consist of clumps of heavy traffic separated by clear space.
You'd have to quantify whether staying in the clump was more dangerous than moving through it; without that, you can't really make a determination one way or another.
Works on I-95 often enough; that's a pretty major highway. And it works most of the length of it, in my experience; I bet it works on a lot of highways. The time travelled in the clear is mostly the speeder's choice; once he's moved through the clump he can sit in the gap for a while.
Roads with lights are a different issue. There, you can't win if you don't play, but if you get ahead one light cycle, you can win big -- and buttuming you're not sluggish at acceleration, there's no real downside to trying to do so.
You can't easily maintain proper following distance in a clump. People will cut in in front of you, even if they don't want to go any faster. So you have to constantly slow down to maintain the distance.
PAC-MAN is winnable.
