9.7.6.7 Ctm Cell

Occupancy

For CTM links (or TS), this mode shows CTM cell occupancy at each cell for the current point in the cycle time as set via the Animation Controls screen. The width of each blue block is proportional to the occupancy of that cell. (Control the width scaling of the blocks via the NetCon Options screen.)

As you change the timeline via the Animation Controls screen, the cell occupancy blocks will move through the network, and in this way you can easily visualise the movement of traffic through the network. Blocking back effects are also easy seen.

Use the Interpolate Values option to give a smoother animation.

In the screenshot below, the link at Node 3 from the south is a pedestrian link. Because of the way cell occupancy is calculated, this link appears to have a very large occupancy in its cell closest to the stop line. This is because the maximum occupancy of each cell is proportional to the link or TS saturation flow, and the pedestrian link has an arbitrarily high saturation flow. Of course it is questionable to considerable what 'cell occupancy' represents in the case of pedestrians, but, you can interpret it as showing a large pool of pedestrians waiting at the crossing point - which is intuitively true, since pedestrians do not generally wait in line back from the crossing point. The same would be true of any stream of traffic with a large saturation flow; and conversely for a stream with a very low saturation flow.

The resolution of CTM cells is determined by the number of time steps in the model and the cruise speed of each link.

If the Stop line Saturation flow has been set to be different from the Cell Saturation Flow for a link or TS, you will notice the difference between the width of a full cell at the stop line compared with the rest of the CTM cells.

9.7.6.8 Ctm Cell Flows

This mode (activated using the PDM/CTM Cell Flows option) shows CTM cell flows at each cell in each CTM link or TS for the current point in the cycle time as set via the Animation Controls screen. The width of each cyan block is proportional to the occupancy of that cell. (Control the width scaling of the blocks via the NetCon Options screen.)

Larger blocks show where the highest flows occur at the current point in the cycle. They will be largest on links or TS with the highest flows, and at times where these links or TS are discharging the maximum amount of traffic, e.g. when a queue begins to dissipate.

It may often be easier to visualise the flow by showing them at the same time as the cell occupancies. An alternative appearance is available by selecting CTM/PDM Cell Flow Arrows, which will use arrows for flows instead of blocks. In the screenshot below signal states are also shown and the diagram clearly shows the location of traffic, the signal states shown to traffic at the stop line and the areas of heaviest flow. Note that flows are shown at the upstream ends of links or TS on red up until the point where queuing traffic begins, at which point the flows diminish to zero.

CTM Source Cells

This mode will show red and green circles at the entry point of each CTM link or TS. Red circles on the entries indicate that the CTM occupancy and queue on the link or TS is greater than it can accommodate and that therefore traffic will be queueing before it enters the network.

Other toolbar buttons

Use Show/Hide Background/Diagram to choose between showing the Network, the background image(s) or a combination of both. Selection can be achieved either using the drop down list (click on the down arrow) or by clicking on the icon itself to toggle between the options.

Use Fast Mode to turn off certain textual items to increase the drawing speed.

Other buttons on the main toolbar at the top of the NetCon window let you choose whether to display bend-handles, connectors, show stop lines (see section 9.5) and to turn on and off a layout grid.

The screenshot below shows the effect of turning these items off and choosing a larger connector arrow size via the NetCon Options screen.

Stop lines of signalled links are represented by black square brackets, located at the downstream end of each link.

NetCon Options screen

There are a large number of options controlling the appearance of NetCon, and you can access these via the NetCon Options screen. (Use the icon on the right-hand side of the main toolbar or right-click in NetCon and select Tools>Options).

Most items are self-explanatory and are not listed here other than the ones of particular interest below. Most tabs have a Defaults button, which will restore the options on that tab to their default values.

Most NetCon options are saved in the data file, so the same options will be used when you next load the file.

Please also see the main TRANSYT Preferences screen for other options that may affect NetCon.

Setting a background image

Add one or more background images via the Backgrounds tab. Press the Add button and then browse to a bitmap (bmp/gif/jpg format), which will then be placed in the middle of the NetCon diagram. To adjust the opacity, position and size of the image, you must select it in the list box. The image will then be shown with a red outline and red handles in NetCon, which you can use to move and resize it. Use the opacity slider to control how faint the image is relative to the rest of the diagram.

You can add more than one image. For example, you may have several drawings of junctions which you can superimpose on the diagram at the same time as an overview map. Adjust the opacity, position and rotation of each image so that they overlay the relevant links and nodes in the TRANSYT network.

The images are embedded in the main TRANSYT data file; there is no need to save the image files separately.

Showing textual data

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Multiple "Text Sets" can be defined to store user preferences for displaying text on traffic streams and links using the Texts tab. A single "Default Layout" is already set up in TRANSYT in any new file. This can be adapted or other sets can be added to it. Buttons are provided to add, delete and rename sets.

Within each set, settings for both link text and traffic stream text are defined. Sub tabs are used to set the data items separately for links and traffic streams. There are four positions where data can be displayed on traffic streams and five positions on links. The data displayed can be any TRANSYT data field (i.e. any input data or output results).

For traffic streams, a data field can be shown at both ends (positions A and C), in the middle (B) and also in front of the stop line symbol (E). Select the data fields to use by clicking on them in the Data Editor (or a Data Grid) and then clicking the Select Field button. Alternatively, click on the dropdown arrow next to the Select Field button to use the data tree structure instead. Tick the Enabled box to actually show the values on the diagram.

Similarly any data field can be shown on each link by setting up options in the Link Text sub-tab - A data field can be shown at each corner of each link (A, B, C and D) as well as in front of the stop line symbol.

^ ^ Each "text set" can be selected using a button on the toolbar, either using the down arrow to select or clicking on the symbol to toggle through each of the available sets.

Changing the foreground and background colour

The foreground and background colours can be changed via the Other tab of the NetCon Options screen. A dark background and a light foreground can be useful for high visibility visualisations.

Other NetCon Features

Use user arrows on each link or TS to show turning proportions without necessarily having to set up actual connectors or exit links. Right-click on the link or TS and select from a left, straight or right user movement. The movement will be depicted using a blue arrow at the stop line.

You can show two or more NetCon windows at the same time, using one for an overview of the network, and one as for close-ups of individual nodes.

There are options in the User Preferences screen to control the way that directions for arrows are calculated. ⁴

Working with Analysis Sets, Demand Sets and Time Segments

NOTE: The system of Analysis Sets and Demand Sets used in TRANSYT 14, although looking similar, differs from that used in ARCADY.

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J Analysis Sets allow you to store multiple sets of data within a single file, representing, for example, different signal plans and flows for AM and PM peak periods.

Demand Sets allow you to store different sets of flow data, which can optionally be combined together. Each Analysis Set uses a single Demand Set, but this Demand Set can reference any number of other Demand Sets.

Time Segments are used when using TRANSYT with more than one time segment specified. For example you can run the TRANSYT model over a 60 minute period using 4 time segments of 15 min each. Flows can optionally be entered for each time segment, or you can set up TRANSYT to produce flows automatically; in either case, a set of results will be available for each time segment, along with a set of overall 'summary' results representing the entire 60 minute period.

NB do not confuse Time Segments with Time Steps. Time Steps are used internally to control the resolution of the model on a per-cycle basis and are independent of Time Segments.

The current Analysis Set, Demand Set and Time Segment are always shown at the top of the main window. Click on the icon next to each one to jump to the appropriate part of the Data Outline where you can edit the definitions. The same icons are used throughout the Data Editor and other screens to indicate where a data item is entered or is available for each Analysis Set / Demand Set / Time Segment.

To change the current set, select it via the appropriate drop-down list. Any screens that show data for each set will then automatically update.

Make sure you understand the distinction between editing the definitions of Analysis/Demand Sets versus editing the actual data for each set. E.g. you may have an AM Peak and PM Peak Analysis Set, each of which contains a separate set of data. Edit the data via the normal data entry screens, making sure that you have selected the correct Analysis/Demand set via the drop-down menus on the main program toolbar.

The current analysis set and current demand set is also indicated by the presence of an asterisk in the Data Outline, as an additional reminder of which sets will be used when you run the file. For Demand Sets, this is not necessarily the same set as you are editing/viewing at the time, as it is the specific Demand Set referenced by the current analysis set that is run.

When you add a new Analysis Set or a new Demand Set, the new set contains a copy of all the data for the previously selected set. E.g., all traffic flows for the new Demand Set will be a copy of the flows for the last selected Demand Set.