I recently had a customer asking how Civil 3D determined how to adjust profiles when locking them together to build an intersection. Specifically, what if you had a constraint in place for the secondary road profile (travel at –2% for 100’ from the main road centerline, for example.) Does the main road profile move to match the secondary road profile, or does the secondary road profile arbitrarily move to match the main road profile? As it turns out, you have options here, you just have to know where to go to set them. Find out more after the jump.
A lot of people forget where some very important settings are stored – in the command settings of a given Civil 3D object. We can find out a lot about how intersections are created when we edit the command settings for the CreateIntersection command. You can find this on the settings tab of Toolspace by expanding Intersection, then Commands, then right clicking CreateIntersection. Doing this will bring up the following dialog:
If you look closely, you will see options for how the secondary road profile is treated:
Here, we can set both maximum grade, maximum grade change, and set up distance rules. So in my example above, you would set your maximum grade to –2%, and your distance value to 100’ – this will allow us to meet the requirements for the intersection without worrying about what’s happening to the secondary road profile.