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Link Curves

By defining curves for certain links, you can give the network plot a more true-to-life representation. With M2Assistant, you can define a curve for any link in the network by simply dragging one of two control points for any link.

The following plots are from the standard Winnipeg Demonstration database. The first plot shows a portion of the network without curves. The second plot shows only those links that are curved while the third plot shows all links including those with curves. 


Standard Links


Links with curves (plot created using the IsCurve link keyword)


Curved Links (press Ctrl-K to switch between showing curved and straight links)

To define links with curves, first open the Links layer properties (Ctrl-Alt-P), and check the Show link curves and Edit link curves check boxes. The Tolerance property is used to limit when curves are to be displayed. If the distance (in screen coordinates or equivalent printer coordinates) between the the I node and J node of a link is less than the Tolerance, then the link is displayed as a straight line. 


Close the link layer properties and then click on a link. When the Edit link curves check box is set, two control points are shown in green that are equally spaced on the link. 


Move the mouse over either green control point and click and drag the point. A bezier curve will be drawn with the control points for the curve being four points on the link, the I and J nodes, and the two control points that you can move around. Move one or both of the control points that are shown in green until the link curve appears correct. Press F5 to refresh the plot. 


If the Show link curves check box is set, the link will be drawn as a curve.


To unselect the link, either click another link to select it, click an empty space on the plot or clear the Edit link curves check box. You may also delete the link curve information by clicking the curved link, right-clicking the mouse, and choosing the Delete Link Curve... menu option. This does not delete the link, it just deletes the curve information for the selected link.

Some information about how M2Assistant uses and maintains curve information for the EMME/2 database is as follows:
  • Link curve points are stored in a file named M2LinkCurve.m2a which is created in the same folder where the EMME/2 database resides. No curve data is stored in the EMME/2 database.
  • The file stores the I-Node number, the J-Node number, and the coordinates of the two control points for the link. Only links for which you have defined curves are stored in this file. 
  • The link curve information is not scenario specific. This means that all scenarios must have the same link I and J node numbers for curved links.
  • A link curve applies to both directions. Therefore only one link curve record is maintained for both the I->J and J->I directions of the link.
  • The link curve is used by the link layer, path layer and transit segment layer. The transit line layer does not use link curves.
  • The IsCurved link keyword can be used in a link Filter Expression to show only those links which have curve information.