Need help in creating a road with an outer radius of 12.5m and inner curve radius of 5.5m with a width of 3.5m

[jragruta]

From the title, Need help in creating a road with an outer radius of 12.5m and inner curve radius of 5.5m with a width of 3.5m in civil 3d.

An indicative of this is shown in this image. I have tried offsetting a line by 3.5m and using the fillet command on the first line by 12.5m and 5.5m on the offsetted line. However it doesn't seem to be similar in the image.

Am I missing something? Sorry for asking.

[nkiakas]

Hi @jragruta 

In the attachment as i understood is your swept path

The outer (or inner) line of your swept can't be the road design (alignment) due to the "sharp" geometry

I suggest you to do the below step by step

1. Create the alignment of the centerline (CL) like the green one in the sketch. "Play with radii in your turn, it depends from the classification of your road, because i see you design track is a bus maybe the design speed can be max 50km/h. Means you can use Radii with range 5 to 15m. Because you require outer 12.5 and inner 5.5 i assume that your correct radius will be 9m.
2. Create 2 offsets alignments (the yellows in the sketch) left and right with the width you prefer. The radii of the offset alignments will be selected automatically based on you width of each lane
3. Select one by one the offset alignments and from the properties change them from dynamic to static.
4. Delete the curve from each alignment from the alignment tools
5. Add a curve between 2 tangents for each alignment according to your requirements (12.5m and 5.5m)

Please note that offset alignment(s) is a nice dynamic tool. When you change the geometry of the centerline, the offset alignments are following the new geometry. But from the step #3 and later you will lose this ability.

[nkiakas]

Hi @jragruta

i forgot the attachment in previous reply. Its below