Traffic engineering (transportation)

Traffic engineering deals with the functional part of transportation system, except the infrastructures provided.

Also, traffic flow and speed sensors are used to detect problems and alert operators, so that the cause of the congestion can be determined, and measures can be taken to minimize delays.

Observation on limited access facilities suggests that up to a maximum flow, speed does not decline while density increases.

However, above a critical threshold (BP, breakpoint), increased density reduces speed.

Therefore, speeds and lane flows at bottlenecks can be kept high during peak periods by managing traffic density using devices that limit the rate at which vehicles can enter the highway.