Scenario management

Scenario management allows you to manage related networks in a single project. The aim is to model comparable cases in these networks and then compare their simulation results. For each case within a project, you create a separate network that is saved as a scenario. You then change each scenario according to the requirements of the respective case. Then you configure the desired evaluations and perform simulation runs for the scenarios whose simulation results you want to compare.

Basic Elements - Overview

Scenario Management is primarily based on the following elements:

Base network

If you place an *.inpx network file under Scenario Management, Vissim creates a new scenario management project based on the Vissim network of the network file and generates a base network including a first scenario (Placing a network under scenario management). The base network may already contain a modeled network or be empty (Opening and editing the base network in the network editor). You can derive additional scenarios from the base network. Make sure the entire base network has been modeled and simulation runs trouble-free before you place it under scenario management and derive a scenario.

Avoiding changes to the base network and carrying them out under modifications

Vissim automatically adopts changes made to the base network into the derived scenarios. Therefore, do not change the base network from which scenarios are derived and, if necessary, edited, as different changes made to the base network and scenarios can lead to conflicts. These conflicts may, for example, result in Vissim no longer being able to load individual modifications and scenarios, as their changes can no longer be considered. If changes to the base network are necessary, add a new modification, make the changes to it, and in the Loading sequence position, select the last position for its assignment to the desired scenarios (Editing the project structure). This way possible conflicts only arise during this modification. This allows you to delete the modification from the scenario and restore the previous status of the scenario.

Scenario

A scenario is a changed version of the base network or of another scenario within a project (Opening and editing scenarios in the network editor). A scenario contains the changes you made in the form of modifications. You can use a scenario to perform simulation runs.

Modification

A modification contains changes made to a scenario, with the aim of creating different requirements for a simulation run than those in other scenarios whose simulation results you want to compare. Within a project, scenarios differ from the base network through one or multiple modifications. The scenarios of a project differ from each other through several modifications (Opening and editing modifications in the network editor). Within a project, you can assign a modification to different scenarios or deactivate the assignments made. Do not make changes to the base network. Edit the scenarios only.

Project

The following elements are managed in a project:

• Base network
• Scenarios based on the base network
• Modifications that distinguish the base network from its scenarios as well as the scenarios from each other.

When you place an *.inpx network file under scenario management, Vissim creates a new project and a first scenario. The Vissim network of the *.inpx file becomes the base network of the project (Placing a network under scenario management). A project and its scenarios and modifications are displayed in the project explorer (Using the project explorer). In Scenario Management, the length of the path to the project directory is limited to 214 characters (Technical information and requirements).

Examples of use

Example of use 1

In your Vissim network, you want to compare the impact of different volumes of an area of investigation during rush hour times in the morning and evening.

You create a new project based on your Vissim network. Vissim saves your network to the project as a base network and automatically creates a copy of the base network called scenario 1. In scenario 1, you define the traffic volumes for the morning. You then duplicate scenario 1 and rename it to scenario 2. In scenario 2, you define the traffic volumes for the evening. You configure the desired evaluations, perform simulation runs for both scenarios and compare the results.

After evaluating the simulation results, you can make changes to the base network and scenarios, duplicate or delete scenarios and perform simulation runs.

Example of use 2

For several PT lines, you want to compare the impact of changes to their route and their time distribution. To do so, you want to change base data, the location of network objects in the network and various attributes of network objects.

You create a new project based on your Vissim network that includes the initial situation of the PT lines. Vissim saves your network to the project as a base network and automatically creates a copy of the base network called scenario 1. In scenario 1, you change the requirements of your use case, namely the route, distribution times, network objects and base data. You then duplicate scenario 1 for all other use cases. You can rename these duplicates. In each duplicate, you change the requirements according to the respective use case, i.e. the route, additional network objects and base data. You then configure the desired evaluations, perform simulation runs for the individual scenarios and compare the simulation results.

After evaluating the simulation results, you can make changes to the base network and scenarios, duplicate or delete scenarios and perform simulation runs.

Managing projects and editing attributes of base networks, scenarios and modifications

You manage a project, including base network, scenarios and modifications in the project explorer and the project structure (Using the project explorer), (Project explorer toolbar), (Editing the project structure). The project structure also allows you to edit attributes of the elements. You cannot undo a function executed in scenario management. By default, an undo function is available when you model Vissim networks.

Editing base networks, scenarios, and modifications in the network editor

In the network editor, you can open and edit all scenarios and modifications (Opening and editing the base network in the network editor), (Opening and editing scenarios in the network editor), (Opening and editing modifications in the network editor). However, avoid changes to the base network to avoid conflicts with derived and edited scenarios (Avoiding changes to the base network and carrying them out under modifications). In the File menu, in the list of files last opened, you can select the base networks and scenarios last opened in the network editor (if the file path has not been changed).

If in several scenarios, you subsequently create or edit network objects of a network object type and these network objects have the same number in the different scenarios, this may affect the simulation as well as the comparability of the simulation results.

Tip: Alternatively, in the project explorer, right-click Base network, Scenario or Modification, and on the shortcut menu, click Open.

Numbering network objects

In various scenarios of project, the values of the Number attribute of network objects of a network object type may be identical. This allows you to easily identify the same network objects in different scenarios and compare simulation results referring to these network objects. When you define a new network object in a scenario, by default Vissim suggests a value for the Number attribute that is not used in any other scenario for a network object of the same network object type. You can accept the value suggested or enter a different value.

If you add new network objects of the same network object type to different modifications of a scenario, Vissim avoids identical numbers and proposes an individual number for each one. This ensures that you can use the modifications in a scenario without causing conflicts due to identical numbers of network objects of the same network object type.

Comparing scenarios

You can compare the attributes and attribute values of network objects of an opened scenario with those of other scenarios (Comparing scenarios of the scenario management).

Calculate multiple scenarios automatically in a row

You can select multiple scenarios and have them automatically calculated one after the other (Project explorer toolbar). You can do the same for all scenarios.