Traffic modellers need queue length surveys to measure delays and congestion at junctions. They can be carried out for one or more of an intersection's arms. When multiple lanes are present, the data for vehicles in each separate lane or in only the longest queue can be recorded. This is often needed for traffic modelling to ascertain whether the junction is efficient or whether a junction improvement scheme is needed.
Queue length at junctions may be measured in vehicle numbers or in meters or yards depending on which is specified.
The number of vehicles in the queue as the red traffic signal changes to green may be recorded, or data may be collected at regular intervals such as every five minutes.
Queue length surveys are often carried out in conjunction with turning count surveys.
Queue delay surveys at junctions may also be carried out. These involve recordings vehicle arrival times and departure times at the intersection. Manual observation techniques are often used for queue surveys.