While the average queue length reflects the capacity of traffic signals, the so-called 95th and 99th percentile of queue lengths at red ends are used for determining the length of turning lanes, such that the risk of a blockage in the through lanes could be minimized. Moreover, lengths of back-of-queue (queue length at the Queue – end) must be considered for determining the lengths of turning lanes at signalized intersections. The queue lengths and their distribution can be numerically calculated. The percentiles of queue lengths can be estimated from the distribution.
If a bus or heavy vehicle was present within the first eight vehicles of the Queue during a signal cycle, then a Queue was cast out. Two observers were assigned to each intersection, with each responsible for two approaches. During a one-hour period, each observer alternated fifteen-minute periods between their two approaches. A review of field sheets has been taken place for accuracy, and a common difference was noted. On several cycles, it was noted that the vehicles did not queue as expected. Examples include the following: • A vehicle would leave a space between the automobile in front equal to a car length for no apparent reason. A vehicle would leave a space between the automobile in front equal to a car length to avoid blocking a driveway. The lead vehicle in the Queue would pull up significantly beyond the STOP line.
Queue length Surveys provide detailed secondary information relating to the length of queues that vehicles on each arm are experiencing at a specific intersection at certain peak times of the day; it is an excellent accompaniment to an intersection count. As always, we undertake these surveys using H.D. video cameras. Depending upon the client’s requirement, we can supply different queues. This includes maximum Queue & minimum Queue in any interval, Average queue length, Queue at the start of the Green phase and Queue delay surveys, etc. We even have experience of tracking the Queue back from one exit of the motorway to the other using multiple cameras.