Use the criteria-based design feature to apply agency-specific standards to an alignment.
The criteria-based design feature provides the ability to verify that your alignment design meets the minimum standards required by your local agency.
When you use the criteria-based design feature, you can select a design criteria file, from which you can specify criteria such as the attainment method and minimum radius and transition (transition) length tables. When you lay out the alignment, the appropriate minimum values specified in the design criteria file are displayed on the command line. You can either accept the default minimum value for a given sub-element, or specify a new value.
Minimum transition length values are automatically generated using the specified curve radius. If there is no curve associated with the transition, then the minimum value is the smallest acceptable transition radius.
If the design parameters for a sub-entity violate the minimum values established in the design criteria file, a warning symbol appears both on the sub-entity in the drawing window and next to the violated value in the Alignment Entities vista and Alignment Layout Parameters window. When you hover the cursor over a warning symbol, a tooltip displays which standard has been violated and how to correct the violation. The display of the warning symbol is controlled by the alignment style.
You can generate a report that documents validations or violations in the alignment design. The design criteria report identifies whether each sub-element within a given chainage range violates or meets the appropriate design criteria and design checks.
After an alignment has been created, you can check that the elements are straight to one another.
Design Criteria Files
The design criteria file contains the minimum design standards for alignment and profile objects. You can customize the design criteria file to support local design standards for parameters such as transition length and minimum radius.
Design criteria files containing standards in both metric and imperial units are included with Autodesk Civil 3D.
If your local agency standards differ from those in the supplied design criteria files, you can use the Design Criteria Editor dialog box to customize the file to support your local standards.
Some alignment design criteria are not available in table form in the design criteria file. For these criteria, you can define design checks to validate design standards. To apply a design check to an alignment, you must add it to a design check set.
Specific design criteria files are available for road and rail applications. The Rail alignment type cannot use the road design criteria file, and the Centerline, Offset, and Corner Radius Alignment types cannot use the rail design criteria file.
The road design criteria file can also include criteria to support automatically adding widening around curves to dynamic offset alignments.
Alignment Design Criteria
A design criteria file can contain the following alignment design criteria:
- Minimum radius at a given design speed
- Attainment method
- Superelevation rate at a given radius
- Minimum transition length for a given radius Note: Compound transition length is not validated against the design criteria file. You must use design checks to validate compound transition length.
- Automatically adding widening to dynamic offset alignments. (Road design criteria files only.)
Profile Design Criteria
A road design criteria file can contain standards tables for minimum K values at specified design speeds. Minimum K values for the following distances are available:
- Stopping Sight Distance
- Overtaking Sight Distance
- Headlight Sight Distance