This is kind of neat, in a geeky way. It's a traffic simulator that allows you to model things like ring roads, on-ramps, etc., while controlling for variables like traffic lights, ramp inflow, composition (car/truck ratio), speed limits, delta-B ramp (no, I have no idea what it means, either) and even a "politeness factor."
In just a few minutes, you, too, can create massive, paralyzing gridlock.
At least, that's what I did with it.