Gridlock

Gridlock is a type of traffic jam where "continuous queues of vehicles block an entire network of intersecting streets, bringing traffic in all directions to a complete standstill". The term originates from a situation possible in a grid plan where intersections are blocked, preventing vehicles from either moving forwards through the intersection or backing up to an upstream intersection.

The term gridlock is also incorrectly used to describe high traffic congestion with minimal flow (which is simply a traffic jam), where a blocked grid system is not 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 across an intersection. This traffic is then stopped, by sometimes too much capacity for the roadway or an accident, blocking the intersection. The drivers in the other direction then go into the blocked intersection trying to get through. In many jurisdictions, drivers are prohibited from entering an intersection at a green light if there is no room for them to clear the intersection. 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 that block intersections.

Another type of gridlock can occur during traffic surges between highway on-ramps and off-ramps located within a quarter mile of each other. Traffic exiting the highway may back up and block the entering vehicles.

Gridlock is sometimes cited as an example of the prisoner's dilemma (from game theory). 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 equal cooperation.

In New York City, drivers who "block the box" are subject to a moving violation that comes with a US$90.00 penalty. Mayor Michael Bloomberg, noting that the ten-minute ticketing process actually contributes to overall traffic congestion, has recently asked the New York State Legislature to remove “blocking the box” from the moving violation category. This reclassification would give more traffic agents authority to write tickets and change the current ticketing procedure, which requires that the issuing officer physically stop the violating car in traffic.

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Wikipedia