The Frontiers crew travels to Los Alamos to investigate this question. Physics and high-tech traffic simulations on supercomputers provide the answers.
Simulation is used to understand traffic patterns and design more efficient, workable roads.
In fact, a project in Oregon is attempting to simulate an entire city and its population. A propagating wave disperses its energy across a medium. As the wave disperses, it continues to spread out. In the traffic example, when one car slows down momentarily, it creates a backward wave that affects the cars behind it. Computers like those at Los Alamos are used to simulate events from nuclear wars to terrorist attacks and, now, traffic.