YouTuber Brick Technology (previously at Neatorama) built a LEGO traffic simulation as a miniature version of Yuki Sugiyama's full-size traffic experiment on what causes traffic jams. While this involves a round track with no intersections or turns, the results are similar to what we may encounter in real life.
First he has to build a track using magnetic guidance, and then the trucks. They are programmed to act either like human drivers or robot drivers in the way they accelerate, slow, and stop. The results are dependent on the density of traffic, because one too many trucks will slow them all down. Then he throws in confounding factors: one drunk driver, then a real human with a controller, and finally he raises the speed limit. It's all chaos by the end. You might get the idea from this that robots drive better, but keep in mind there are no pedestrians or animals wandering onto this track. -via The Awesomer