I would like to see graphs showing the relationship between different geometric parameters and capacity results – in previous versions these were a useful tool in teaching newer users about the sensitivity of certain parameters.
Can you give the model a range for a parameter and then do a quick test to see how it affects RFC?
Questions such as these can easily be investigated by using the Analyser Screen in Junctions 9.
- To start, click the Analyser button at the bottom of the main vertical toolbar.
- There are some built-in graphs which can be used to quickly produce graphs showing how queues for example vary as traffic in the junction is increased. To use these graphs, click the Common X-Y graphs link at the top-left of the Analyser Screen and then choose one of the options. This will populate the rest of the screen. You can then click the Line button in the top-left corner to generate the graph.
- Graphs are produced by performing lots of runs of the traffic model, with the item of interested being varied according to the range and steps specified, and forming the x-axis of the graph. Points are plotted in a random order, so that you can quickly see the shape of the graph without having to wait for it to build up from left to right. Each point involves running the traffic model, so the time taken to produce the graph depends on how complex the file is.
- There aren’t any built-in graphs that involve varying geometric parameters, but the x-axis and y-axis can be anything in the file, so you can easily create such a graph by following the steps as in the following example.
- The upper panel in the Analyser Screen contains the Input Variables, which form the x-axis of the graph. The panel can contain several items but only one can be selected at any time. Use the Remove button at the bottom of the panel to remove any existing items. Then, to add a new item, browse to that item in the file. E.g. go the the roundabout geometry screen and click on Entry Width. The Input Variables panel should then contain a button towards the top, similar to “Add Arm 1 – E – Entry Width”. Click on this and that variable will be added to the list of variables and you can adjust the range and step size.
- The lower panel contains the Output Variables, which form the y-axis. This panel can contain several items and ALL selected items will be plotted. You can add items in a similar way to that described above. E.g. go to the whole period results for Arm 1, click on the RFC, and then click the Add button towards the top of the Output Variables panel. To add the RFC for all other arms, you can add the RFC for each other arm individually using the same process, or, as a shortcut, you can use the “Add all arms/streams” button. A colour will be set automatically for each output item but you can adjust these by double clicking on the colours.
- Once the input (x-axis) and output (y-axis) variables have been set up, click on the Line or Bar buttons at the top of the Analyser Screen to generate the graph.
- If the graph is empty, it may be because the file can’t be run. For example, you can only run a graph where the Entry Width varies if the arm has a non-zero flare length.
- Once a graph has been generated, you can right-click on the diagram or on the table of numbers and copy them to the clipboard.
TIP: If your file uses Lane Simulation mode, then graphs can be slow to draw. In this case, try going to Data Outline>Options>Lane Simulation Options and entering the Stop Criteria Time as a small number such as 4 seconds. This will limit the time taken to run the simulation, meaning that the graph will generate much more quickly – although may show a lot of ‘noise’.
For full details of the Analyser Screen and the other modes it offers, please see the User Guide.