The vs | plus part in the control unit consists of the two main parts parameter and core.
Without parameters, the core does not know what to do. Without the core, the parameters cannot switch any signals.
As you can see from the following figure, the parameters and the core are divided into individual sections and are processed sequentially.
Figure 19: Interaction vs | plus core and parameters
vs | plus is called once per second in most control units. Technically, it is also possible to call vs | plus several times per second.
- The current programme number is also transmitted with the start command of the control unit for vs | plus.
- The programme number is required for the parameters in order to provide the correct data set.
- The programme definitions define which parameters vs | plus should use. For example, up to 8 data sets can be parameterised for the traffic stream parameters. This enables you to cope with different loads throughout the day.
- When vs | plus is started, some preliminary work is carried out first. This includes, for example, checking whether the control unit has already executed the desired switching of the signals and whether the final state has been reached. The aim is to track the vs | plus internal states.
- Next, the inputs are analysed. This requires the information from the control unit and the corresponding parameters. Depending on the situation, each of the checked inputs is checked for request or extension. The detector parameters of the currently valid data set are used for this.
- Once the inputs have been analysed, this information is used to process the traffic streams. Traffic stream parameters are also available in this step. These can be used to set the behaviour of each traffic stream. If a traffic stream is green, the extension of the assigned detectors and the maximum permissible green times can be used to decide whether the green is extended or not.
- The control is divided into two parts. The first part determines which traffic streams are switched on and off. The rank-dependent control parameters are used for this. The traffic streams that can extend their green are processed with those that have a request. At the end of this evaluation, it is clear who gets red or green. This check takes place every second. This means that vs | plus can overturn decisions that were made a second ago, for example because an emergency vehicle has registered.
- The second part of the control is about supplementing the decisions made. Are there traffic streams that should also be switched to green, but have no request? Depending on the parameterisation, these are also switched on. This can be used, for example, to always switch on a parallel, not conflicting pedestrian traffic stream with the IT.
- All decisions in vs | plus have now been made. The decisions at the traffic stream level must now be converted into switching commands for the signal groups or digital outputs. The transition parameters are used for this. The individual signals are transmitted to the control unit at the correct time based on the intergreen time. This completes the work for vs | plus. Only with a new start command from the control unit is a new assessment of the situation made by vs | plus.