From Wikipedia, the free encyclopedia

Gridlock is a term describing an inability to move on a transport network. The term originates from a situation possible in a grid network where intersections are blocked, prohibiting vehicles from moving through the intersection or backing up to an upstream intersection. This is illustrated below on a network of one-way streets (the red cars are those causing the gridlock by stopping in the middle of the intersection).

The term gridlock is also widely used to describe high traffic congestion with minimal flow (a "traffic jam"), whether or not a blocked grid system is involved. By extension, the term has been applied to situations in other fields where flow is stalled by excess demand, or in which competing interests prevent progress.

The traditional form of gridlock is caused by traffic heading in one direction blocking cross traffic at an intersection. In many jurisdictions, drivers are prohibited from entering an intersection if they cannot clear it before the traffic light turns red. If drivers follow this rule of the road, gridlock will be prevented and traffic will only be slow in the direction that is actually congested. One method of reducing gridlock is to aggressively enforce penalties for vehicles which block intersections.^[1]

Gridlock is sometimes cited as an example of the prisoner's dilemma (from game theory).^[2] Mutual cooperation among drivers would give the maximum benefit (prevention of gridlock), but this may not happen because of the desire to maximize one's own benefit (shortest travel time) given the uncertainty about the other drivers' commitment to cooperation.

The first appearances of the word gridlock in newspapers occurred in 1980, during a transit strike in New York City. The word is attributed to Sam Schwartz, who was the chief traffic engineer for the city's Department of Transportation at the time of the strike.^[3] Schwartz said the word gridlock was used internally in his department during the 1970s, perhaps as early as 1971.^[4]

• Box junction
• Roadway air dispersion modeling
• Deadlock - computer software analogy

1. ^ Stringer, Scott M. Thinking outside the box: an analysis of Manhattan gridlock and spillback enforcement, Office of Manhattan Borough President, July 2006.
2. ^ Heath, Joseph (1999). Normative economics, Chapter 2, Section 3. Retrieved on March 19, 2007.
3. ^ Schwartz, Sam. About Gridlock Sam, GridlockSam.com. Retrieved on March 19, 2007.
4. ^ Popik, Barry (July 21, 2004). Gridlock. Retrieved March 19, 2007.