Accounting for Driveways and Ramps in AutoCAD Civil 3D Corridors

I thought I’d blow the dust off of an old topic because I’m finding that many folks out there are not accounting for driveways in their corridor. It is fairly simple to add driveway features or even handicap ramp features to a corridor without splitting regions and utilizing additional assemblies. By using a conditional assembly, this can easily be accomplished.

The conditional subassembly called ConditionalHorizontalTarget serves as a type of IF statement in your assembly: “If this object exists at this assembly location, then do this; otherwise, do that.”

The subassembly will look for a polyline, feature line, survey figure, or alignment to trigger this behavior.

The subassembly must be inserted on the assembly at the marker point where the change will occur. Before clicking on the marker where this will be placed, address the Parameters in the AutoCAD Civil 3D Properties palette as follows:

• Side: Usually, the subassembly can pick up what side it’s inserted by the marker point picked. This value represents the right or left side of the assembly.
• Layout Width: This does not apply to the design, shape, or appearance of your corridor. This simply affects how this subassembly will appear to the user in the assembly.
• Layout Grade: This does not apply to the design, shape, or appearance of your corridor. This simply affects how this subassembly will appear to the user in the assembly.
• Type: The subassembly will be inserted twice at the same marker location. One instance of the subassembly’s Type parameter will be configured as Target Found and the other will be configured as Target Not Found. This is how you tell the corridor what to do in either instance.
  
• Maximum Distance: This value will limit how far out to look for the target within the side it is assigned to. The default is 9999’ which is fine in most cases unless your alignment forms an arc, in which case you may want to shorten the default distance; if you can project a line perpendicularly off the alignment and intersect the alignment at another location, you probably need to shorten the Maximum Distance to an amount less than that line.

After placing the conditional subassembly twice, it should look like this:

Notice how much physical room it takes up? This is where configuring Layout Width and Slope may save you some space. Below shows the same assembly after reducing the layout parameters.

Starting with the Target Not Found version of the subassembly, add the subassemblies that determine what happens when the driveway is not there. In this example, the curb/gutter and sidewalk were added.

For the Target Found version of the subassembly, insert the subassemblies that determine what happens when the driveway is there. In this example, two generic LinkWidthAndSlope subassemblies are used:

• The first matches the gutter slope and width.
• The next matches the flowline elevation of the gutter and is set at a slope to match the back of the sidewalk.

To finish off the conditional subassembly configuration:

• Click on the Target Not Found subassembly, right-click, and click on Subassembly Properties.
• On the Information tab, in the Name field, type the letters Not after the subassembly name. This will help you to discern this subassembly in the Corridor Properties Target Mapping dialog.

The above pictured subassembly configuration can be copied to other assemblies using the Copy tool on the Modify Assembly panel of the Contextual ribbon. If you have already built your entire corridor, consider turning Rebuild Automatic off.

To prepare the plan for the new assembly configuration, the targets must be created where the driveways intersect the location in the subassembly where the conditional subassembly has been placed; in this case, it’s the edge of pavement.

• Create two layers dedicated to hold the targets for the right and left side of the corridor.
  
• Set the right target layer current and create polylines at the right driveway locations. Polylines are quick and easy to create, so create polylines across the driveways. Consider setting a width so you can easily see which driveways you’ve accounted for.
  
• Set the left target layer current and create polylines at the left driveway locations.
• When finished, your results should look something like this:
  

 

To add the targets to the corridor, do the following:

• Select the corridor, then from the contextual ribbon, click Corridor Properties (click on the top half of the button).
  
• In the Corridor Properties dialog, click Set all Targets in the top right corner.
  
• On the Offset and Elevation tab of the Target Mapping dialog, scroll down until you see the ConditionalHorizontalTarget. Hold the Ctrl key down and click on each of the Target Offset entries for the right side of this subassembly.
  

 

Using Civil 3D 2023, you can now filter columns in the Target Mappings dialog.

• Click on the Subassembly column heading. Select the column to filter.
  
• Then click on the Side column and select the column to filter.
  
• Next hold down Ctrl-A to select all filtered regions.
• In the bottom portion of the Target Mapping dialog, go to the right pane labeled Select feature lines, polylines, and survey figures to target and click on the checkbox next to your driveway layer(s) to fill it. Notice that the values in the Offset column have been changed from to **Varies**.
  
  
• Click OK to the Target Mapping dialog.
• Click OK to close Corridor Properties. Notice the driveways are now defined in the corridor.
  
• Repeat this section for the left side of the corridor to complete.

 

Achieving an accurate design in a reasonable amount of time is key in completing our virtual work on a site. Using tools that allow us to maintain elements that are dynamic with our design building blocks will keep our model up-to-date and error free. Basic corridors make all this possible, and implementing conditional subassemblies allows us to apply alternative changes in our sections without creating new regions and inserting new assemblies.

– Cyndy Davenport