Discussion on the influence of different phase sequence on coordinated control

1、 Typical phase type

According to the different phase control modes, it can be divided into three typical signal control phase types: symmetrical release, single port release, and lap release. Each type has different advantages and disadvantages and scope of application.

1. Symmetrical release

Symmetrical release refers to the release of the traffic flow in a certain direction of an import while releasing the traffic flow in the opposite direction. It can be used when there is a large gap between the straight traffic flow and the left turning traffic flow at the same entrance, and there are similar characteristics in the opposite direction.

2. Single port release

Single port release means that each entrance lane acts as a separate phase, allowing its left turning vehicles and through vehicles to release at the same time. This release mode can be used when there is a large difference in traffic flow at each entrance.

3. Lapping release

Overlapping release integrates symmetrical release and single port release, and there are overlapping release of traffic flow at the same time, such as left turn traffic flow in two phases at the same time. This method can flexibly adjust the release time according to the traffic flow in all directions, and the scope of adaptation is relatively wide.

2、 Phase effect in coordinated control

In the implementation of one-way coordinated control, the influence of phase on coordinated control can be ignored. However, in the two-way coordinated control, it is necessary to realize that both green wave bands fall in the release phase of the inlet channel. At this time, different phases and phase sequences will have a great impact on the effect of coordinated control (or green wave bandwidth).

In the coordination control model (maxband, multiband), a variable (the time of the midpoint of the uplink red light at the intersection and the midpoint of its adjacent downlink red light, referred to as the phase variable) is defined to express the relationship between the uplink and downlink coordination control phases, and this variable is introduced into the optimization solution model, so that the priority coordination control scheme can be found by optimizing the phase sequence of the intersection.

For example, the upstream and downstream release timing of intersection i is shown in the figure below. Let Ki be the time between the midpoint of the upstream red light at intersection i and the midpoint of the downstream red light that is close to it. If the midpoint of the upstream red light is located to the right of the downstream red light midpoint, Ki is positive, otherwise it is negative.

Through this variable, we can get rid of the bottleneck of seeking priority coordinated control scheme only in the dimensions of cycle, speed, green letter ratio, etc., further expand the space for optimization, make the coordinated control scheme more flexible and more adaptable to the coordinated control of various complex road sections and multiple intersections.

3、 Influence of different phase sequence on coordinated control

Through the phase variable, we further analyze various typical phases and draw the following conclusions:

1. Symmetrical release

In the symmetrical release phase, the uplink and downlink directions are in the same phase, the phase variable is 0, and there is no other value. The space for coordination scheme optimization is limited, and the phase cannot be optimized at this time. Therefore, in the symmetrical release phase, it is relatively difficult to achieve coordinated control, and it is also difficult to obtain a better coordinated control effect. However, when there is a large amount of green letter in the coordination direction of the uplink and downlink directions, a certain coordination effect can still be achieved.

2. Single port release

In the single port release, the uplink and downlink directions are in different phases. At this time, by adjusting different phase sequences, the phase variable parameters can obtain different values.

For example, each entrance of an intersection adopts the single port release method. If the east entrance is in the upward direction (green letter ratio 0.3), the west entrance is in the downward direction (green letter ratio 0.3), and the green letter ratio of the south and north entrances is 0.18 and 0.22 respectively, the following phase sequence can be obtained: