Split a corridor and create a road intersection

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Civil 3D provides tools for automatically generating intersections

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where two or more alignments cross.

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They can be used to create standard three- and four-way intersections and roundabouts.

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Intersections update dynamically when changes are made to the connected alignments or profiles.

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They are made up of customizable components

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such as lane configurations, curb returns, and grading slopes

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that make it easy to design for compliance.

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Also, intersections are integrated into the corridor model,

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ensuring seamless connections between road segments and across the road network,

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as well as accurate earthwork calculations.

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After you have a corridor modeled, you can split it into two or more segments,

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and then add the necessary intersections.

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Once the intersection is ready to be evaluated,

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you can use several visual and analytical tools in Civil 3D

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to evaluate the intersection for sight distance.

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In this example, a corridor has already been created in the open Civil 3D drawing.

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The first step is to split the corridor into segments to create space for the intersection.

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In the drawing, select the corridor model.

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Then, from the contextual ribbon, Modify Region panel, click Split Region.

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The program prompts you to select the region of the corridor to split.

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In the drawing, select the region, and then select the specific split location.

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Now, zoom in to the selected point and use the grips to create an opening by dragging the arrow,

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making space for the intersection to be modeled.

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Ensure that both alignments intersect each other,

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zooming in to examine the intersection closely.

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If needed, extend the alignment beyond the main alignment

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to make sure that there is a definite intersection.

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Now that you have a definite intersection and a profile for both the main road and the side road,

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you can build the intersection.

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From the ribbon, Home tab, Create Design panel, expand Intersection and select Create Intersection.

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In the drawing, zoom in and select the point where the alignments intersect.

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Then, you are prompted for the main road alignment.

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Press ENTER to open the Select alignment dialog.

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Select the appropriate alignment, and then click OK.

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The Create Intersection wizard opens.

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Specify the intersection name, marker style, and label.

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Then, expand the Intersection corridor type drop-down

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to select whether the intersection corridor should maintain the primary road crown or all crowns.

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Select each option to update the preview, and in this case, select All Crowns Maintained.

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Click Next to set the offset parameters.

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If you want the offset roads to follow existing alignments,

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you can specify them here.

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In this case, skip this step.

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Click Next to choose the assemblies to apply.

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If you previously created assemblies for that intersection, you can use those,

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or you can use the default assemblies suggested, as in this case.

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Click Create Intersection.

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The wizard closes, and after a moment, the drawing updates to display the intersection.

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If the labels are overlapping, click and drag them out of the way for a better view,

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to ensure that the intersection appears correct.

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Here, you could connect the road on the right to the intersection,

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but leaving a gap will enable a smoother transition between the point codes and daylights

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when creating the surface from both corridors.

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Now you know how to split corridor segments and create intersections in Civil 3D.