If you’d like to create design checks for profile tangents, hopefully this post will save you the time and headache that I went through to get something that works. I learned some pretty interesting stuff. Find out after the jump.

1. The parent alignment must have a design speed assigned for design checks to function at all.
2. Civil 3D does not like it if you go back through a data reference and assign a design speed to the parent alignment after the profile’s already been created.  Had to delete the profile and redo after assigning design speed to the DREFed alignment.
3. {Tangent Grade} is a decimal value so 12% = 0.12 (should have known that)
4. ABS (and I’m assuming other functions) do not affect C3D properties like {Tangent Grade} so I had to use an IF/THEN to test whether the grade was > or < 0.
5. Formulas are inconsistent in the way >= and <= are interpreted.

After battling all that, I finally have design check formulas that will check min and max grades on profile tangents:

IF({Tangent Grade}<0,{Tangent Grade}>-.1201,{Tangent Grade}<=.12) Will tag anything with a grade greater than 12% (positive or negative)

IF({Tangent Grade}<0,{Tangent Grade}<-.00499,{Tangent Grade}>=.005) Will tag anything with a grade less than 0.5% (positive or negative).

Have fun!