The pre-signal system adds an additional stop line with a pre-signal at the upstream of the intersection arm, which forms a tandem traffic signal system. The entire (or partial) lanes between the pre-signal stop line and main stop line can be named “sorting area.” kinase inhibitor All the vehicles that entered the sorting area will be reorganized by the pre-signal. As illustrated in Figure 1, the vehicles heading for the same direction will be distributed laterally in the sorting area. The pre-signal

usually operates on the same cycle as the main signal. The queued vehicles at the pre-signal will enter the sorting area based on the green phase of pre-signal alternatively. By the time the main green starts, all lanes of the sorting area can be utilized to discharge vehicles during both through and left-turn phases. Left-turning vehicles and throughput vehicles are asked to form tandem batches and parade through the sorting area as well as the intersection cross-section using all lanes. Compared with the traditional design of the intersection, adding the pre-signal system can significantly improve the utilization of the temporal and spatial road resources, especially at congested status. Although the theoretical capacity may drop and the delay will increase after setting the pre-signal system, the traffic flow dynamic can be more effective at the

congested intersection sorting area. For the same traffic signal scenario, previous experiments indicated that the pre-signal system with well configuration can increase the capacity of an

intersection approach with three lanes by 15–50% [8, 9]. Meanwhile, the greens of the pre-signal can be optimized by the main signal or real time queue information of the sorting area to ensure the queue is discharged within the main green [10]. The detrimental effect like De-facto red can then be avoided by using the pre-signal system. On the other hand, the security of the traffic dynamic at the intersection approach can be improved as the vehicles run orderly. Figure 1 Components and classification of the pre-signal system. The pre-signal system can be classified according to the usage of the sorting area. Anacetrapib If all lanes between the stop lines of pre-signal and main signal are considered as sorting area, the pre-signal system is a full utilization type. The sorting area of part utilization type does not include all the lanes of the intersection approach. The pre-signal system can also be classified by the queued vehicles within the sorting area. As shown in Figure 1(a), if the vehicles heading to different directions queued in the sorting area serially, the pre-signal system is a multimovements type. Similarly in Figure 1(b), if the queued vehicles in the sorting area only head to one single direction, it can be considered as a single movement type. The design of pre-signal system is flexible.