The term gridlock, coined by the Traffic Department in New York City in the 1970s, originally referred to a specific effect of traffic congestion in cities with a grid layout: Drivers with a green light could not fully pass through the intersection before their signal turned red, thereby blocking traffic in the cross direction from proceeding when the light turned green in the cross direction. The use of the term gridlock has subsequently been broadened to refer to any traffic congestion (including highways) in which stop-and-go movements or periodic complete stops are the norm rather than the exception, whether or not a gridded roadway network is involved. Gridlock imposes costs on human lives and the environment in many ways: It wastes fuel, adds to commuting ...