Perpendicular Offsets

[NeilSpoon]

Further to my post on the general board:

http://forums.autodesk.com/t5/AutoCAD-Civil-3D/Footways-with-Offset-Assembly/td-p/3329025

I would like to see an easy way of creating perpendicular corridor offsets from channel lines (offset alignments) that are not parallel to the main alignment. This is often the case in road widening at junctions etc. Please see the attached image.

Now you either have offsets that are perpendicular to the main alignment only, creating back of footpath lines that are not the width specified in the subassembly (measured perpendicular to the channel line, as it should be), as well as crossfalls applied diagonally accross the footpath, which gives inaccurate levels. The width issue can be sorted with a target line, but this is an extra step which shouldnt have to be taken.

The only way I can see how you can design this properly, is by adding an offset assembly to the channel (EC) and attaching the curb & footpath subassembly to that. However, the offsite alignment (channel) needs to be specified in Corridor Parameters for the OFFSET and a profile needs to be created for this (which, as far as I can see, needs a temporary surface of the road, so levels can be applied).

This seems a bit of a long winded approach for something so basic in road design.

My wish would be either or, even better, all of the below:

• The possibilty of a subassembly that enables anything attached to it to be offset perpendicular from it. (Like a subsidiary string in MX)
• That superelevation specified for the main alignment is projected to any offset alignments attached to the main alignment, enabling the offset alignments to have a profile instantly which is dynamic to the main alignment. (how this is not possible is slightly baffeling me).
• If an offset assembly is attached to a subassembly, it should be dynamic to that point. So if the road gets widened, the offset alignment stays attached to the edge.

But point no. 2 would be my main request. Surely this is a simple thing to programme in? The offset alignment is already dynamic horizontally?

Anyway, just some thoughts 🙂

[jmatthei]

Agreed.  This would be a great enhancement.  Also (maybe) related--a way to handle bullnose ends of islands in roadways, short of giving up and feature lining them.

[peterfunkautodesk]

You could do this right by using a "Marked Point" and "Link to Marked Point"

1. Make the main part of the road using the offset alignment as a target.

2. At the edge of pavement, add a Marked Point and give it a name (EOP)

3. Add an offset assembly

4. Add a "Link to Marked Point" sub assembly using the name set in 2

5. Add side walk etc to the Link to Marked Point SA

What this does is sets the elevation (and offset) location of the edge of the main line. The offset will then tie into this point for the elevation (the offsets in this case are the same).

Make sure that you turn off the display of the link so that it doesn't draw up from 0.

You don't need a profile for the second alignment.

Regards,

Peter Funk

Autodesk, Inc.

[fcernst]

Thanks, this would have saved me from having to create underlying corridor reference surfaces that I had to profile for the edge of travel way (ETW) on my roads to get the Offset Assembly concept to work. I had to use the Offset Assembly because I had a project with road widening (various long traffic calming widenings) and couldn't get the ditch to go perpindicular to the ETW. I wasn't pleased with having to do this extra workaround procedure.

Again, thanks for the "workaround", but I strongly second the motion that we shouldn't have to use an Offset Assembly to achieve perpinduclarity for such things as ditches and sidewalks. I'd say it's a peculiarly obvious shortcoming of an otherwise great product!