The main purpose of traffic signal phase is to properly separate the conflicting or seriously interfering traffic flows and reduce the traffic conflict and interference at the intersection. Traffic signal phase design is the key step of signal timing, which determines the scientificity and rationality of the timing scheme, and directly affects the traffic safety and smoothness of the road intersection.
Explanation of terms related to traffic signal lights
1. Phase
In a signal cycle, if one or several traffic streams obtain the same signal color display at any time, the continuous complete signal phase in which they obtain different light colors (green, yellow and red) is called a signal phase. Each signal phase periodically alternates to obtain the green light display, that is, to obtain the “right of way” through the intersection. Each conversion of the “right of way” is called a signal phase phase. A signal period is composed of the sum of all phase time periods set in advance.
2. Cycle
The cycle refers to a complete process in which various lamp colors of the signal lamp are displayed in turn.
3. Traffic flow conflict
When two traffic streams with different flow directions pass through a certain point in the space at the same time, traffic conflict will occur, and this point is called the conflict point.
4. Saturation
The ratio of the actual traffic volume corresponding to the lane to the traffic capacity.
Phase design principle
1. Safety principle
The traffic flow conflicts within phases shall be minimized. Non conflicting traffic flows can be released in the same phase, and conflicting traffic flows shall be released in different phases.
2. Efficiency principle
The phase design should improve the utilization of time and space resources at the intersection. Too many phases will lead to the increase of lost time, thus reducing the capacity and traffic efficiency of the intersection. Too few phases may reduce efficiency due to severe collision.
3. Balance principle
The phase design needs to take into account the saturation balance between the traffic flows in each direction, and the right of way shall be reasonably allocated according to the different traffic flows in each direction. It shall be ensured that the flow ratio of each flow direction within the phase is not much different, so as not to waste the green light time.
4. Continuity principle
A flow direction can obtain at least one continuous green light time in a cycle; All flow directions of an inlet shall be released in continuous phases; If several traffic streams share the lane, they must be released simultaneously. For example, if the through traffic and the left turn traffic share the same lane, they need to be released simultaneously.
5. Pedestrian principle
In general, pedestrians should be released together with the through traffic flow in the same direction to avoid the conflict between pedestrians and vehicles turning left. For intersections with a long crossing length (greater than or equal to 30m), secondary crossing can be appropriately implemented.
Post time: Aug-30-2022
