This was a great question this morning and definitely worth a video to capture the processes to use to add in draiange points into road pavement surfaces. The point here is that the road may have a standard -2% cross slope but at the locations where drainage structures exist the cross slope typically increases a bit into the structure. The -02% then may transition to say -3% at the structure and then back to -2% again after the structure, or you may be given a specific elevation to tie into, or you may be given a grade into the structure or out of the structure etc.
Vertical design allows you to use any of the following rule types to handle the situations that the engineer throws at you including
- Specify an elevation at the structure and you define where the transition In and out of the structure starts and ends
- Specify a slope into the structure from Centerline and you define where the transition in and out of the structure starts and ends
- Specify a sag curve at the structure to smooth the transition in and out of the structure
- Specify a grade rule along the flow line to transition into the structure
In addition if you have a -2% slope on the pavement and a -4% slope into the flow line, and then a 0.5’ elevation step up to Top Back of Curb, when you modify the pavement for the drain you likely don’t want to modify the top back of curb elevation because of the drain - so sequence of instructions is really important but again vertical design handles this really well
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