To ensure Allsite tools can reliably build and maintain roading networks (Road Corridors, intersections, knuckles, cul-de-sacs, sharp bends), corridors must be created using a consistent Civil 3D workflow. This section describes the supported approach and the minimum setup required before running the Civil 3D Intersection Wizard.
Note - you can run Level AI without road corridors (using Allsite's Layout Assist), for this follow instructions here.
Run the 'Validate Corridor' tool to validate the DWG and road corridors within it meet Allsite requirements for Level AI / Service AI.
Main Workflow
Supported methods and current limitations
Road Corridors
Corridors can be created using standard Civil 3D alignments and assemblies.
Assemblies
Allsite requires specific usage of sub assemblies, this includes the usage of lane sub assemblies only for the road lane. Outside of the actual road use link or sidewalk sub assemblies.
Custom sub assemblies can cause issue as sometimes the geometry cannot be read. Review points are added if there are any issues with usage of custom sub assemblies. If custom sub assemblies are required, ensure they have the word "Lane" or "Curb" or "Sidewalk" in their name.
Offsetting the central subassemblies from the assembly itself is not supported (will result in minor discrepancy in levels)
Custom combined sub-assemblies are not currently supported by Allsite.ai (support may be added in the future).
Allsite.ai does not currently support custom combined sub-assemblies. Support may be added in future.
Alignments
Road centreline alignments are drawn as normal.
Do not extend alignments past the end of a cul-de-sac or T-intersection. Overrun geometry can cause issues—trim alignments to the road region end.
Prerequisites (before intersections)
Allsite requires that each road centerline alignment has:
An Existing Ground profile, and
A Design profile (preliminary design is fine; commonly a manual straight-line design profile), and
A corridor created with regions, and
The corridor’s vertical baselines explicitly set to use the design profiles.
Only after this is complete should you run the Civil 3D Intersection Wizard.
Step-by-step required workflow
1. Create road centerline alignments
Create your road centerline alignments as usual.
Confirm alignments are trimmed correctly at dead-ends/intersections (no overshoot).
2. Create profiles for every alignment (Existing + Design)
For each centerline alignment, create:
Existing Ground (EG) profile
Design profile (preliminary is acceptable; manual straight-line is supported)
You can do this manually, or use the Allsite tool that loads profile views and creates both profiles (EG + Design).
3. Create corridors with regions
Create a corridor for the alignments using standard assemblies.
Ensure the corridor is built with regions (do not leave the corridor as a single undefined region).
4. Set vertical baselines to use the Design profiles (required)
Use the Allsite tool for setting vertical baselines.
Confirm each corridor baseline is using the intended design profile as its vertical baseline.
Critical:
If design profiles are not set as the vertical baselines, curb return profiles may lose or fail to maintain links to the offset alignments’ profiles when vertical baselines change.
Intersections need Side Road Profile Grade Rules DISABLED (Set to Not Apply) to avoid corridors corruption. Initializing the project will disable this setting only for subsequent intersections. How to disable.
5. Only then: run the Civil 3D Intersection Wizard
With corridors built and vertical baselines correctly assigned, you can now create intersections reliably.
Note: Best practice recommendation (even if using connected alignments/profiles)
Civil 3D intersections created with connected alignments + connected profiles generally maintain more robust relationships.
However, Allsite recommends still creating and assigning preliminary design profiles first, then setting them as vertical baselines, before running the intersection workflow. This reduces profile-link instability and keeps corridor behavior predictable as edits occur.
Validate your drawing before Level AI / Service AI
After corridor setup (and anytime you make major edits):
Run Allsite → “Validate Corridor”
This checks that the DWG and its road corridors meet Allsite requirements for Level AI / Service AI.
The Allsite AI Assistant will provide guidance on how to resolve any issues.
Road Network Features