Traffic management methods
All signal-controlled junctions in Vilnius City are managed adaptively (in accordance with the current transport flows) in order to use the time in the junctions as efficiently as possible and to ensure that the traffic flow capacity is as high as possible. Moreover, the traffic situation is periodically monitored and evaluated; upon receiving the results of conducted analyses, changes of signal control and management programs are made.
In order to understand the principles of traffic signal control systems, we have to know the methods of traffic management.
The real-time changes of the junction’s signal program that are dependent on the transport flows, i.e. the duration of the green light changes in every light group depending on the number of vehicles detected by the transport sensors.
“Hard” mode of junction operation
The mode of operation when the junction operates in accordance with a pre-determined signal program and the duration of the green light is exactly defined for every light group. Over the span of 24 hours, several “hard” signal programs for junctions can be used, e.g. morning rush hour, daytime, evening rush hour, and night-time signal programs.
MOTION (Method for the Optimization of Traffic signals In Online-controlled Networks) is a method of real-time traffic optimization. After receiving data on transport flows from junction controllers, the server of the Traffic Management Centre calculates the most optimal signal program and the phase times for each junction.
Complete adaptivity of the junction
A junction operation mode when the duration of the green light is directly dependent on the transport flows in the junction. The minimum and maximum time limits are set for each phase, while the cycle time is not significant. This operating method is applied in the junctions that are further away from other signal-controlled junctions.
Partial adaptivity of junctions, combining junctions into a green wave
A junction operation mode when the duration of the green light is partially dependent on the transport flows but there are strictly defined limits regarding the point of the cycle time at which each phase must turn on. Contrary to the case of complete junction adaptivity, here junction synchronisation requires the cycle time, as otherwise a green wave is not possible in the entire junction corridor. Each phase in the cycle has to be turned on at a strictly defined time. Phase duration changes in each cycle depending on the transport flows. For this method of junction operation, 4 main signal programs are typically used: the morning rush hour, daytime, evening rush hour, and night-time.
Partial adaptivity of junctions, combining junctions into a green wave using MOTION method
This method is very similar to the partial adaptivity of junctions when junctions are combined into corridors and a green wave is created. The difference is that, after receiving data on the transport flows, the server of the Traffic Management Centre calculates (generates) new signal programs for each junction every 6 minutes. In this case, the number of signal programs for the entire day is not defined and varies depending on the changes in transport flows. Junctions are synchronised according to the principle of the partial adaptivity method: significant factors are cycle time and the limits of when each phase is turned on.