Traffic congestion is a conition on any network as use increases and is characterized by slower speeds, longer trip times, and increased queueing. The most common example is for physical use of roads by vehicles. When traffic demand is great enough that the interaction between vehicles slows the speed of the traffic stream congestion is incurred. As the demand approaches the capacity of a road (or of the intersections along the road), extreme traffic congestion sets in, where vehicles are fully stopped for periods of time, is colloquially known as a traffic jam.