Signalization

Signal controllers can be allocated to nodes and main nodes. There are various types of signal controllers: signal group based, phase based, RBCs (ring-barrier controller), and external signal controls (Vissig). In the case of signal-group signal controllers, signal groups can be defined immediately. In the case of stage-based signal controllers, stages must be defined first, and after that, signal groups can be allocated to the stages. Vissig controls are managed with an external program (External controls).

Note: For further information on RBCs, please refer to the RBC manual in the Doc\Eng folder of your Visum installation directory.

Signal controllers can be switched off. In this case, nodes and main nodes for which the signal controllers have been switched off are treated as two-way stop nodes in procedures such as ICA and signal time optimization. Switching off a signal controller will thus change the node control type.

Note: A signal controller can be allocated to multiple nodes or main nodes. However, this is only recommended for Vissig controls, as the procedure Signal cycle and split optimization only delivers good results for multiple nodes and main nodes in combination with Vissig controls. The number of the coordination group of the signal controller plays a role in the Optimization of the signal controller offset operation (User Manual: Creating a signal coordination group).

The key attributes of a signal group are its Green time start and its Green time end. These attributes are relevant to the node impedance calculation (Signalized nodes). In external controls, signal groups can have two pairs of green time start and green time end. Thus, you can model a second green time, represent it correctly in the signal time display of the network editor, and take it into account in the node impedance calculation. In case of stage-based signal controllers, green time start and green time end of a signal group correspond to the green time start and green time end of its stage. If for a signal group or stage, the Green time start attribute is 0 and the Green time end attribute is identical with the signal controller cycle time, this is interpreted as permanent green. Both attributes are restricted by the cycle time of the signal controller. The Green time end can have a smaller value than the Green time start. In this case, the green time is calculated by subtracting the difference of both values from the signal controller cycle time. The green time cannot fall below the minimum green time of a signal group.

If for a signal group or stage, the Green time start attribute is 0 and the Green time end attribute is identical with the signal controller cycle time, this is interpreted as permanent green. Both attributes are restricted by the cycle time of the signal controller. The Green time end can have a smaller value than the Green time start. In this case, the green time is calculated by subtracting the difference of both values from the signal controller cycle time. The green time cannot fall below the minimum green time of a signal group.

Signal groups also have the attributes Amber, , and Allred. Furthermore, you can define and edit Intergreens between signal groups. All of these values are important when calculating the signal cycle and split optimization. Hereby, the Used intergreen method attribute of the signal controller determines whether the amber and all-red time or the intergreen matrix are used for optimization. The ICA loss time adjustment attribute is used in the calculation of the impedances with ICA to determine the effective green times with the aid of the specified green times. The Minimum green time attribute is used for signal cycle and split optimization, serving as a low threshold value for the green time calculated. The Vissim coordinated attribute is only relevant for the Vissim export.

The connection between the signalization and the network is established by allocating the signal groups to lane turns. Each signal group can be allocated to any number of lane turns. Prerequisite is, that the lane turns are located at nodes or main nodes which are allocated to the signal controller of the signal group. Likewise, any number of signal groups of the signal controller can be allocated to each lane turn that is allocated to the node or main node of the lane turn. A signal group can also be allocated to any number of crosswalks. A crosswalk, however, can only refer to one signal group. The data model is not restricted here. As an example, Visum does not check whether a signal group is allocated to each lane turn. It does not check either whether conflicting volumes have overlapping green times. Should the signalization be used to determine node impedances, it is recommended to carry out the respective ICA network check option to detect incomplete junction models (User Manual: Checking the network and fixing errors).

Note: It is recommended to complete the modeling of a node or main node, before allocating signal groups to lane turns. When deleting or inserting lane turns, the signal control data can get lost.

External controls

A special feature of external signal controllers is that the data is not saved in the version file. Vissig control files are saved in the *.sig format. This way, they can also be accessed by other programs, for example Vissim. To edit external control data in Visum, you use the Vissig program. In external controls, multiple signal programs can be stored. This is not the case for signal group based or stage based controls. Therefore, the signal controller attribute Signal program number is only relevant when dealing with external controls. Visum accesses the data saved in the control file at certain times. This is, for example, the case when opening a version file or when running the operations Signal cycle and split optimization and Update impedances at node via ICA.

Note: Up to Visum 12, RBCs belonged to the external controls. Now RBC files in the *.rbc format are still read in but are no longer used.

Stage templates

Stage templates can be used to easily generate signal control data at a node or main node (User Manual: Editing the signal times of stage-based controls). If a stage template is allocated to a node, the signal controller of the node then possesses a lot of stages and signal groups. Lane turns are already allocated to the signal groups. This means, for example, that conflicting volumes are signalized with different green times.

Note: A prerequisite for the use of a stage template is, however, that a stage-based signal controller is already allocated to the node or main node.