Using Design Criteria Files

As you did with alignments, you can assign design criteria files to a profile. The general behavior of design criteria files is the same as it is for design checks: they display warning symbols when certain design parameters are not met. However, behind the scenes, design criteria files are much more sophisticated than design check sets, and you can use them to check more types of geometric criteria.

To apply a design criteria file to a profile in your drawing, complete these steps:

The Exercise File can be downloaded at the end of the article  

1. Open the drawing named Design Criteria File.dwg located in the Chapter 07 class data folder.

2. Click the Jordan Court FGCL profile, and select Profile Properties on the ribbon.
3. Click the Design Criteria tab. Check the boxes next to Use Criteria-Based Design and Use Design Criteria File.
4. Click the button to the right of the file path, and select the file named Autodesk Civil 3D Imperial (2004) Roadway Design Standards.xml (Autodesk Civil 3D Metric (2004) Roadway Design Standards.xml). Click Open.
5. Verify that the box next to Use Design Check Set is unchecked.
6. Click OK. New warning symbols appear on several of the vertical curves.
7. Hover your cursor over the warning symbol farthest to the left. The tooltip reports that minimum passing sight distance is not being met (see Figure 7.11). Since passing will not be allowed anywhere within the subdivision, this warning can be ignored.

   Figure 7.11  Warning symbol with tooltip reporting that the passing sight distance criterion is not being met.

8. Hover your cursor over the warning symbol at the lowest point of the profile. Notice that this curve is not meeting the requirement for minimum headlight sight distance. This is a requirement that should be honored.

9. Click the Jordan Court FGCL profile, and then click Geometry Editor on the contextual ribbon tab.

10. On the Profile Layout Tools toolbar, click Profile Grid View.
11. In Panorama, scroll to the right until you can view the Minimum K For Headlight Sight Distance column. Note that a warning symbol appears in the row for Item 6 and that the required K value is 26.000 (9.000), as shown in Figure 7.12.

    Figure 7.12  A warning symbol in Panorama indicating a violation of the headlight sight distance criteria.

12. Scroll to the left until you can see the K Value column. Change the K value for Item 6 to 26 (9). This removes the warning symbol and changes the curve length to 215.128 (74.914). To practice good design, you’ll round that value in the next step.
13. Change the Profile Curve Length for Item 6 to 225 (75). This generates a K value of 27.193 (9.010), so the warning symbol is still suppressed.

What’s So Special about K?

The K value is a way of expressing the abruptness of a vertical curve. If you’ve ever been driving on a country road and caught air at the top of a hill or smacked your head on the dashboard at the bottom of a hill, then you’ve experienced a K value that is too low for your speed. The K value is calculated as a ratio between the curve length and the change in grade. Longer, more subtle curves have a higher K value, which equates to greater safety because the change in grade is spread out over a longer distance.

Headlight sight distance is an important design parameter for all road designs. If the peaks and valleys of the road do not allow headlights to illuminate obstacles within an acceptable distance, then the road is considered unsafe. The acceptable distance varies based on design speed. Obstacles need to be detected much farther away at higher design speeds to allow the driver enough time to react.

Using Design Check Sets and Criteria Files

• Using Design Check Sets
• Using Design Criteria Files

Download Exercise File :

• C07 - Design Check and Criteria - Metric     --- ( 1.97 MB )
• C07 - Design Check and Criteria - Imperial  --- ( 1.8 MB )