The junction properties windows is shown whenever a new potential road junction is detected. For example, when the end of one road is placed on or near the carriageway of another. It is also shown when you select to modify a junction.

Create a New Junction

To create a junction of two roads you simply use the road design tools to place the end of one road on (or near) the carriageway of another. Both roads must have some carriageway width as specified with the Create Channels function.

Note: A road may junction onto its own carriageway if you design it to loop round back into itself.

As soon as the roads are placed in a position where a junction would be possible, the Junction Properties window is shown, offering to create the new junction and displaying a preview how it would look.

Junction Edit Properties window

Edit an Existing Junction

You can edit the properties of an existing junction by selecting the Junction Tools button junction tools toolbar. Click the Edit Junction button edit junction button, and then click near an existing junction on the plan view.

Junction Properties window

The junction properties window displays a preview of the junction.

Left/Right Junction Radius

The left/right junction fillet radii are shown in boxes next to the corresponding arcs on the preview. You can enter your desired fillet radii, and the preview will update to show how the junction would look.

Perpendicular Junction

It is often desirable to design the incoming road to join perpendicularly at the junction. Accordingly, when the join is not perpendicular Site3D displays the joining angle in the top left of the preview window.

Non-perpendicular junction indicator

This is purely for your information and does not prevent the creation of a non-perpendicular junction.

Create/Update Junction

Click the Create Junction or Update Junction button to accept the junction. The junction will then show on your road design, fully calculated in 3D according the levels and gradients of the two joining roads.

No Junction

When the Junction Properties window has been produced for a possible new junction you can choose to decline the junction by clicking the No Junction button.

No Junction option window

You then have the option to decide that the terminating road should never junction (to stop it asking again if you edit it later). Whichever option you choose, you can always change the road's termination property in the Road Properties window.

Remove Junction

When editing an existing junction, you have the option to remove it completely by clicking the Remove Junction button. You can always change the road's termination property in the Road Properties window, if you need to later re-create a junction at the end of this road.

Undesirable Junction Detection

Occasionally a potential junction will be offered which appears badly formed.

Undesirable junction example

For example, where two roads meet very close to their ends it is not always obvious (to the software) which road should junction into which. In this example, the longer road is attempting to junction into the shorter road. Because the longer road bends sharply northwards just at the junctioning point, one side forms an undesirable result.

In this case, the engineer's intention is that the shorter road should junction into the longer road.

If you should see something like this, then you can click the No Junction button. Then further junctioning possibilities will be offered so that you get the one that was wanted.

No Junction confirmation window
Desired junction offered

After selecting No junction for the first offered junction, the next potential junction for the two roads is offered. In this case it is the correct solution for the engineer's intention, with the shorter road junctioning into the longer road.


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