VISSIM - PC MOVA & Scenario Management
Introduction
Welcome to the latest Modelling Group blog post.
At Modelling Group, we undertake many projects which require the use of TRL’s external signal control application, PC MOVA, for replicating MOVA signals in a VISSIM environment.
For this post, we are going to focus on the interaction between PC MOVA & Scenario Management and provide some thoughts and tips, based on how we work with both of these features in VISSIM. We hope you find this useful.
Background
The traditional way to configure MOVA signals in VISSIM is to create a PC MOVA connection file and map the detectors in the MOVA dataset to those loaded from the INP/INPX file in VISSIM. An example of this is shown in Figure 1.
PC MOVA & Scenario Management
However, since the introduction of Scenario Management in VISSIM 8, we have come across an issue whereby if you add or amend a PC MOVA controlled signalised junction in a modification file (for us within a scenario), the changes do not show up when creating or editing a PC MOVA connection file. This is because PC MOVA can only read the INP/INPX file (or ‘Base Network’ in Scenario Management) and not any associated modification files.
To get around this issue, there are a couple of options available:
1) For the scenario which features the new/updated signalised junction changes, export the scenario using ‘Project Explorer’ to create an INP/INPX file (see Figure 2). This will then allow the detectors to be mapped as in Figure 1.
2) Within the ‘Base Network’, create a dummy link which includes all of the new or amended detectors and link these to a new or existing signal controller. An example of this is shown in Figure 3.
The second option provides a bit more flexibility in being able to continue working in Scenario Manager and not having to export each scenario into separate INPX files.
The PC MOVA connection file can be created as per normal by mapping the detectors and then, when a Scenario is loaded and played, PC MOVA responds to the demands on the detectors and operates the signals accordingly.
This approach suggests that the PC MOVA connection file only needs to link the MOVA dataset to the correct VISSIM detector number, regardless of the link number the detector is located on.
Working Example
To demonstrate that the use of the modification file and detector mapping (Method 2) produces the same performance as exporting to an INPX file (Method 1), we have undertaken a working example. This has used a single junction model which features an improvement that includes MOVA signals. The model has been coded using static assignment, with fictitious flows, turning proportions and vehicle compositions used to populate the model.
The junction modelled and detector mapping are shown in Figure 4.
Both models have been run for results, with junction flows, queue lengths and journey times obtained from the average of 5 random seed runs.
The results of the comparisons of junction flows, average queue lengths and journey times are shown in Figure 5-7.
As can be seen from the results collated, both methods produce exactly the same network performance in terms of flows, queue lengths and journey times.
This gives confidence that the use of modification files and detector mapping is a suitable alternative to exporting to an INPX file, allowing you to continue to use scenario manager for your VISSIM modelling study if this is your preferred method of working.
Figure 1 – Example of Traditional Detector Mapping
Figure 2 – Example of Exporting Scenario for INPX
Figure 3 – Example of Dummy Link & Detectors in Base Network
Figure 4 – Working Example Model Layout
Figure 5 – Junction Flow Comparisons
Figure 6 – Queue Length Comparisons
Figure 7 – Journey Time Comparisons
Summary
We hope this post has helped to provide a bit of insight into a couple of methods available if you have projects involved MOVA controlled signals. Hopefully, there are some elements you can take away and apply to your own models.
Thanks for reading!