SAC - Subassembly with varying lane width without targets !

This post is based on an earlier post made by Bart De Maesschalck from DEME on the Civil 3D Benelux usergroup page.

The challenge is to create a subassembly with the ability to apply a varying width without the need for a target alignment or polyline/feature line.

In this example the transition will be linear... a curved transition can be considered for another post.

The solution lies in the possibilities that SAC (Subassembly Composer) offers. I'm sure there are many ways to get this done, but this is how I did it…

STEP 1: Define the variables you need

• Base width (Width before the transition, also used in subassembly mode)
• Extended width  (Width after the transition)
• Transition length (Length of the transition zon)
• Transition start station (station to start the transition)

STEP 2: Implement this iS SAC

• Create the input variables we have defined in STEP 1.
• Define an internal variables to be able to calculate the real width during the transition (ActualWidth)
• Define the flows and decisions that need to be taken.
  For every assembly insertion of the corridor we need to define if the current station is before, in or after the transition zone.
  
  
  
  
• Calculate the actual width during transition
  
  

 

• Create the geometry for the lane

  

 

STEP 3: Test in AutoCAD Civil 3D

   

   

The Subassembly can be downloaded here: Download LaneWithTransition

 Peter Ingels

Comments

[Steve]

This is a great tool and can be very useful, though in other situations a bit restrictive. We've had something like this implemented for a while now since SAC had come out.

We've taken ours a bit further allowing for variable slope through the region as well, allowing for a transition from say -2.00% to Flat. It's just a slight manipulation in your code to calculate the transitional slope.

Because the lane width/slope transitions can be restrictive (if you have multiple regions in your corridor), it is beneficial to allow for the user to still be able to target a feature line or alignment as needed. But definitely a useful tool.