A breakdown in traffic flow that occurs when vehicle density exceeds the physical capacity of the roadway. In traffic engineering, this state is characterized by high density and near-zero velocity, often propagating backward as a shockwave from a bottleneck or incident.
Heard on the job
The sensors are picking up a massive traffic jam forming on I-95 southbound due to a disabled tractor-trailer.
Related terms
Phantom jam
A traffic bottleneck that forms on a highway without any physical obstruction or crash.
Gridlock
A severe traffic jam where intersecting streets become completely blocked, preventing any vehicular movement.
Clearance time
The duration required for an intersection or road segment to empty of traffic before conflicting movements begin.