gridlock

right|thumb|Gridlock on a network of two-way streets. The red cars are those causing the gridlock by stopping in the middle of the intersection. Gridlock is a form of traffic congestion 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 used incorrectly 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.