Signalization

Signal controllers can be allocated to nodes and main nodes. There are different types of signal controllers: Vissig and RBC (ring-barrier controller).

Note: For more information on RBC controls, see the help section on PTV Vissim PTV Vissim - Using RBC.

Typical fixed time controls are defined in Visum based on Vissig controls. When creating a signal controller, a distinction can be made between Vissig signal group-based and Vissig stage-based. This distinction is only required when creating a signal controller so that either a signal group-based or stage-based signal program is automatically created in Vissig. After creating a signal group-based control, the signal groups must be defined with their green times and then assigned to lane turns. When creating a stage-based control, you can specify the number of stages of the signal controller. Then the cycle time is divided equally among the stages considering a default time for the interstages. In the next step, you create the signal groups and assign them to one or more stages. The green times of the stages can then be changed either by moving individual interstages in the signal times view or by editing the times in the display of the stages. Interstage durations can also be adjusted in the signal times view via the shortcut menu. This possibility can be used as long as the signal groups are switched exactly at the beginning or the end of an interstage. Subsequently, an assignment of the signal groups to lane turns is also required here.

Simple controls can be modeled in Visum in the Junction editor, which contains the following information:

• Cycle time

• Green times for signal groups or stages

• Allocation of signal groups to stages (for stage-based)

• Allocation of signal groups to lane turns

• Intergreen matrix (optional)

All data entered in Visum is synchronized between Visum and Vissig and checked for consistency. Any change to the signal control data causes an update of the signal controller attribute Signal program data, which contains all the information on the signalization of the signal controller. The attribute is a string of type Base64XML. By import and export, the data of this attribute can be converted into *.sig files and exchanged with other systems. By mirroring the Vissig data in Visum – especially the attributes of signal groups and stages – it can be edited in the Junction editor and in lists.

In the case of more complex controls, the changes must be made in Vissig. In Vissig, you can among other things:

• Create additional signal programs

• Define daily signal program lists

• Create more intergreen matrices

• Edit interstages

• Use other signal sequences

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.

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). Signal groups can also 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. For stage-based signal controllers, the green time start and green time end of a signal group typically correspond to the green time start and green time end of the stage(s) to which they are assigned. By moving interstages in the signal times view beyond other interstages, signal groups can be green in stages to which they are not assigned. This is expressed by the effective signal groups of a stage. So it is the signal groups that are actually green in that stage. The reason for a discrepancy of allocated and effective signal groups is the fact that interstages only contain instructions on which signal groups are switched. If the order of the interstages is changed, signal groups can remain unaffected and thus be green in the following stage, although they are not assigned to it. However, this case should be the exception.

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, RedAmber, 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 of the signal group 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.

Stage templates

Stage templates can be used to easily generate signal control data at a node or main node. 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.