Roundabout - Step by step

In Civil 3D, you can quickly create a two-dimensional roundabout that has the following components: the roundabout central area, approach roads, slip lanes, marking and signage.

The Civil 3D Roundabout wizard automates the process of laying out the horizontal design in 2D for your roundabout. The two-dimensional design of the roundabout includes horizontal alignments that can be used for corridor design later in your project. The roundabout also includes pavement markings, striping, and blocks for signage.

Before you can create a roundabout, you will need to double check that the driving direction is set appropriately in the drawing settings. In the Toolspace, Settings tab, right-click the Creating a Roundabout drawing name and select Edit Drawing Settings. On the Ambient Settings tab, under the General collection, check that the Driving Direction is set to the appropriate side of the road, which in this case is the Right Side of The Road. If everything looks okay then click OK to close the dialog. It is important to check the driving direction, as this is used in the wizard similarly as it is used in the Intersections wizard.

You can create a roundabout from any number of alignments; however, you need at least two alignments to begin. Start with the three that you see in the exercise file. Begin on the ribbon, Home tab, Create Design panel. Expand the Intersections drop-down and select Create Roundabout. The command line asks you to select the center point for the roundabout. Pick the ending point of this alignment where all of the alignments intersect each other. Then the command line it asks you to select the approach road. Pick the first alignment going almost due west. Again, the command line asks you to select another approach road or press enter to end the selection. This time, select the alignment going northeast. One more time, the command line asks you to select another approach road or press enter to end the selection. Lastly, choose the only alignment left going southeast. Now that all of the approach roads have been selected, press ENTER to end the command and begin the wizard.

The Create Roundabout wizard appears. There are many settings that you can configure here. You can set the roundabout center point, the outer radius, the apron width, and the marking parameters. You can also determine which site this roundabout goes on, what alignment styles should be used, and the layer that the alignments must to go on. Additionally, you can set the design standard file to use for the roundabout design, and if it should be US Imperial or French Imperial, and which predefined parameters to import. As you select the different items in the wizard, notice that the different areas in the wizard preview highlight.

For the design of this roundabout, select the US Imperial roundabout standard. Expand the Predefined parameters to import drop-down. There are four options to choose from. Select the R=60 option and you can see that the outer radius, circulatory road, and apron width parameters all change. Change this back to R=45 and again, the roundabout parameters change.

If you do not want to use the presets, you could also change the parameters in the Create Roundabout wizard and then save them for later use. First, set the Predefined parameters to import to R=60. Next, make some changes in the roundabout parameters and then you will save it. To begin, open the preset dialog by selecting the plus ( + ) button next to Predefined parameters to import. The Preset dialog appears. For the Preset Name: enter R=50. Set the Circulatory Road Width: to 25. Then set the Outer Radius: to 50, and the Apron Width: to 15. For the Markings parameters, keep them identical to the settings that are in the Create Roundabout wizard by sliding the Preset dialog off to the side and copying the information over. When all of the information is in the Preset dialog, click OKto save and close the dialog and return to the Create Roundabout wizard.

For this exercise, however, use the R=60 parameters. In the Predefined parameters import drop-down, select R=60. Continuing on in the Create Roundabout wizard, at the bottom of the dialog box is an option to select a site or leave it set to none. There is also an option to pick an alignment style, the layer the alignment would be created on, an alignment name prefix, and the alignment label set. Accept the defaults for now, but understand that you have complete control over all those options. When the Create Roundabout wizard is complete, it will create new alignments for the roundabout. Click Next.

On the Approach Roads page, you must first set the default settings for the approach roads, just as on the first page. For this roundabout, make the Predefined parameters to import also equal to R=60. At the top of the page, you can see that the current alignment is set to the North to South approach. Click the Next>> button and now the West to East approach is set as current. You can make changes with each alignment selected individually, or you can make the changes once and then click the Apply to all button. Change the Default connecting radius: to 150, and then click Apply to all. To check this, change alignments by clicking the Next>>button to change to the South to north approach. On this page,you can see that the Default connecting radius has maintained the value of 150. You also have options to set the alignment style, name prefix, layer, and label set for all of the alignments that are approach alignments. Again, you can configure all of these options individually for every approach road, or just set one of them and click Apply to all. At the bottom of the page, click Next>.

This page deals with the Island configuration. As with the first two pages, set the Predefined parameters to import to R=60. As you can see, this page deals strictly with the islands for the roundabout. As you click through the items on this page, you can watch the preview highlight to see which options define what in the preview area for the roundabout islands. By choosing a predefined parameter, you do not have to choose each and every item in the wizard. Once you are done entering in the information for the island, click the Next> button.

The Markings and Signs page is the last page you need to configure the settings in. As you can see, you can select different types of signs and place them at different locations along each individual alignment in the wizard. You can also turn on and off the pavement markings and island tip markings along each individual alignment. If you find that you are going to use the same settings for all of your alignments after setting one of the alignments up, simply click the Apply to all button to take all of your settings that you created and apply them to all the alignments in the wizard. For this exercise, accept the defaults as they are in the Markings and Signs page. Finally, to create the roundabout, click the Finish button.

While Civil 3D processes the roundabout creation, if the wizard encounters any issues, such as overlapping alignments, a warning dialog appears, explaining the issue. Click OK to continue. The roundabout displays in the drawing.

Remember that this is a two-dimensional roundabout. And, be aware that as the wizard created the roundabout, it also created additional alignments. At this point, you could create finished ground profiles for each one of those additional alignments that were created. And then, you could take those profiles and the alignments and place them into a corridor to make this roundabout usable in your design.