Queue length surveys are used to measure traffic volumes, providing evidence of congestion and delays. They are carried out for each lane of each junction arm. The data can be provided either by number of vehicles or in vehicle lengths or class.
A typical queue length survey involves recording the number of vehicles in a queue just prior to the red signal changing to green for one or more legs of an intersection. When there are multiple lanes, the number of vehicles in the longest queue only, or in each lane separately, can be recorded.
Another variation is to have pre-set distance makers and record the times at which the queue meets that marker.
In situations where queues do not clear within a single traffic signal phase, the volume of vehicles remaining at the start of the new red phase can be collected.