Traffic bottleneck

Capacity bottlenecks are the most vulnerable points in a network and are very often the subject of offensive or defensive military actions.

Capacity bottlenecks of strategic importance - such as the Panama Canal where traffic is limited by the infrastructure - are normally referred to as choke points; capacity bottlenecks of tactical value are referred to as mobility corridors.

Traffic bottlenecks are caused by a wide variety of things: Rubbernecking is an example of how bottlenecks can be induced by psychological factors; for example, vehicles safely pulled to the shoulder by a police car often result in passing drivers to slow down to "get a better look" at the situation.

Downstream of the bottleneck, vehicles transition to state D', where they again travel at free-flow speed vf.

Once vehicles arrive at rate A starting at time t1, the queue will begin to clear and eventually dissipate.

On the time-space diagram, a sample vehicle trajectory is represented with a dotted arrow line.

It is a simple matter of taking horizontal and vertical measurements within the region of state D. For this example, consider three lanes of traffic in one direction.

As shown on the fundamental diagram below, speed qu represents the reduced capacity (two-thirds of Q, i.e., 2 out of 3 lanes available) around the truck.