You may sometimes need to re-order the arms at an ARCADY roundabout, for example if adding a new arm which should be inserted between the existing arms.

For example, say you have a roundabout with three arms 1,2,3, and then wish to add a fourth arm between Arm 1 and Arm 2.

Start by adding the fourth arm in the usual way (use the Data Outline to add a new arm, or, right-click on an existing arm in the Junction Diagram and click ‘Add another arm’).  This will add a new Arm 4, which will be positioned after Arm 3.

There are then two ways you can change the arm order, as follows:

  1. In the Junction Diagram, click on the name of the new arm and drag it to the new position.  (Dragging the arm name in this way will rotate the arm around the centre of the junction.)  Then on the main program toolbar click Tools>Set roundabout arm ordering from diagram.  The new arm order (1,4,2,3) will now be reflected in the diagram, in the Data Outline, in all other screens and in the traffic model itself.  In the diagram you may wish to press Auto-arrange to snap the arms to be evenly spaced.
  2. Alternatively: go to the junction’s properties in the Data Outline and edit the Arm Order data field directly.  In this case, you would change the order “1, 2, 3, 4” to “1, 4, 2, 3. You will probably then want to also move the arm’s position in the Junction Diagram (or click Auto-arrange) so that it visually looks correct.

You can of course rename an arm at any time by simply editing its ID or Name.

NOTE:  if the arm order at an ARCADY junction is incorrect, then the traffic model results will be wrong, because the circulating flow calculations will be wrong.

NOTE:  you cannot change the arm order at PICADY junctions; the PICADY arms A,B,C,D are fixed and explicitly represent the major and minor arms.   At OSCADY junctions, in contrast, the arm order and positioning is entirely arbitrary.