An intersection object builds on and manages various object data, including alignments, profiles, corridors, assemblies, subassemblies, and surfaces.
In its simplest form, an intersection object can be created by selecting the location where two alignments intersect. This automatically creates an intersection object in the drawing, and this intersection object is also displayed in the Prospector tree.
Another approach to creating intersections is to first create roadway alignments, offset alignments, and profiles. Once these preliminary design items are in place, you can create an intersection object that utilizes the 3D aspects of these road design geometry components.
Intersections are created from and based on existing AutoCAD Civil 3D objects, which include:
- Alignments (horizontal). Used by an intersection to define the centerlines of the two roads that intersect. Three types of alignments are used in intersections: centerline alignments, offset alignments, and curb return alignments. The centerline and offset alignments are used to define the horizontal geometry aspects of an intersection object.
- Profiles (vertical alignments). Used to define surface and design elevations along a horizontal alignment.
- Surfaces. Used to build surface profiles, and for corridor grading in an intersection.
- Corridors. A corridor can be built automatically to represent the 3D aspects of the intersection. You can also add to this new corridor information to an existing corridor on the intersecting alignment(s).
- Assemblies. Roadway assemblies are required to build a corridor representing the intersection. To build an intersection corridor, you must be able to access appropriate assemblies to build the intersection model. AutoCAD Civil 3D comes with a set of default intersection assemblies that you can use, or you can create your own custom assemblies that have been designed specifically to suit the needs of intersections you create.
- Assembly set. An intersection corridor requires an assembly set, which is a set of assemblies that are designed specifically for a specific type of intersection design. The assemblies included in an assembly set are defined in an .xml file that is referred to as the assembly set file. A default assembly set and assembly set file is included with AutoCAD Civil 3D. You can create an intersection using this default assembly set, or you can create your own custom assembly sets.
- Subassemblies. Subassemblies define the geometry of a corridor section (through an assembly). For example, a typical roadway may be composed of paved lanes on either side of a centerline, a paved shoulder, a gutter and curb, and a roadside grading. These components are defined independently as subassemblies. You can add any type of subassembly to make up a typical assembly, and then apply that assembly for a station range along an alignment.
Intersection objects have their own display style that controls the intersection object marker. Intersection components, such as offset alignments, curb return alignments, and corridors, also each have their own display styles. Before creating intersections, you should be familiar with creating and managing styles and command settings. For more information on intersection styles, see Intersection Styles and Display.
Intersection Object Considerations
It is important to understand the following before you begin creating intersections:
- Using the Create Intersection wizard, you can create an intersection object that contains up to four quadrants.
- If the default intersection assembly mapping and target assignments does not meet your design requirements, you can create the intersection using these components, and then edit the intersection regions manually to satisfy your design requirements.
- If you create an intersection, and then manually edit the intersection corridor regions, those changes will be overwritten if the intersection is regenerated (by clicking Recreate Corridor Regions on the Intersection tab) or by rebuilding the intersection.
- When creating an intersection, targeting (both horizontally and vertically) is done automatically. If you want to change targets, you must manually modify the intersection corridor region(s) using the Corridor Properties dialog box.
- Typically, when an intersection object is created, the following objects are automatically added to the current drawing: intersection object, corridor(s), assemblies, subassemblies, offset alignments, and curb return alignments. However, assemblies, subassemblies, corridors, and profiles are only added if the appropriate options are selected.
Topics in this section
- The Intersection Object
Intersection objects persist in an AutoCAD drawing as objects with the type AeccIntersection.
- Intersection Styles and Display
Intersection object display style is controlled both by a specific intersection object style, and the styles and labels associated with the objects used to create the intersection, such as the intersecting alignments.
- Intersection Collection (Prospector Tab)
Use the Intersection collection in the Prospector tree to access the intersection objects in a drawing. As intersection objects are created, they are displayed in the Intersections collection.
- Intersecting Alignments Collection
Use the Intersecting Alignments collection in the Prospector tree to access the alignments included in the intersection object.
- Intersection Quadrants Collection
Use the Intersection Quadrants collection in the Prospector tree to access details about the quadrants in the intersection object.
- Intersection Collection (Settings Tab)
Use the Intersection collection in the Settings tree to manage intersection object settings, including intersection object styles, label styles, and command settings.