Stationing for road networks?

[LSF]

Hi.

I'm a landscape architect (yes, one of those annoying people who rely on you for all the hard stuff and I'm trying to design a software feature through which one can create station points in a way that is automated or semi-automated.

I've read a fair amount about it, and we covered it a bit in school, but it was always a single road - usually a highway. The same goes for the few professional projects I've done with stationing. I'm pretty sure that I fully understand stationing within this single road context. And I understand that you can start a new stationing scheme where an old one left off via equalities.

But... what I do not understand is how to handle complex road networks with intersections, like a suburban subdivision or downtown street 'grids' (which are seldom regular). Do you use an equality at every intersection or something? I'm hoping you all will tell me that nobody ever uses stations in this context, or if they do, that they only do so for one or two roads relevant to a site-scale project. If they're intended just for highways, it will make this much easier.

I've attached a poorly drawn plan showing the type of situation I'm referring to. It gets even more complicated when you have 5-way intersections and such. The purple lines are roadway centerlines. You can ignore the diagram in the bottom right.

Any thoughts? Thanks very much.

 

[Jbone27 PE]

What software are you working with? Civil 3D?

 

[Jbone27 PE]

Are you asking how to setup your template so it creates your section but recognizes and applies a tie-in at intersections?

 

[Dexman PE PMP]

Short answer is that all roadways will receive an alignment with stationing that is project specific.  Typically we do not set the stationing to lineup at intersections. The stationing is used by the surveyors to help lay it out in the field for the contractor to build. The start point is typically where the project boundary is (where you're tying into the existing system), but can be wherever the designer assigns it to be.

To help differentiate between the roads, the stationing can be manually manipulated to keep each road separate.  Basically (using made up road lengths), Road 1 would start at 100+00+00 and go to 101+25.42.  Then road 2 would be 200+00+00 and go to 201+18.22, Road 3 would be 300+00.00 and so on.  The intersection between roads 1 and 2 would be the intersection of 100+85.44 and 201+05.66, and when you compared their respective long-sections (elevation view), they would both be at the same elevation where they cross.

When using AutoCAD or any other CAD software, this stationing is generated once you produce the alignment.

 

[LSF]

Thanks both. This is not in an existing CAD program that CE's use, but rather an experimental feature yet to be released for another program. I cannot say what the program is until it gets released.

(...)  Typically we do not set the stationing to lineup at intersections. (...)

To help differentiate between the roads, the stationing can be manually manipulated to keep each road separate.  Basically (using made up road lengths), Road 1 would start at 100+00+00 and go to 101+25.42.  Then road 2 would be 200+00+00 and go to 201+18.22, Road 3 would be 300+00.00 and so on.  The intersection between roads 1 and 2 would be the intersection of 100+85.44 and 201+05.66, and when you compared their respective long-sections (elevation view), they would both be at the same elevation where they cross.

This starts to answer my admittedly vague question. (I assume that by '100+00+00' you meant '100+00.00', as you typed it in the 300 example.) So at the intersection you would show station points for all the involved roads? So for a 5-way intersection, you might have 3 station points (1 for each of the roads that 'continue through' and 1 for the road that dead ends)? And I gather this has nothing to do with the street names, and only relates to road hierarchies in as much as the designer chooses to incorporate them into their notations with the ultimate goal of producing a clear document. So in other words, in situations like these, there is not one right answer for how to do the stationing, but the best answer is the one that is easiest to read while maintaining accuracy. Does that sound more or less correct?

 

[Jbone27 PE]

Thanks both. This is not in an existing CAD program that CE's use, but rather an experimental feature yet to be released for another program. I cannot say what the program is until it gets released.

This starts to answer my admittedly vague question. (I assume that by '100+00+00' you meant '100+00.00', as you typed it in the 300 example.) So at the intersection you would show station points for all the involved roads? So for a 5-way intersection, you might have 3 station points (1 for each of the roads that 'continue through' and 1 for the road that dead ends)? And I gather this has nothing to do with the street names, and only relates to road hierarchies in as much as the designer chooses to incorporate them into their notations with the ultimate goal of producing a clear document. So in other words, in situations like these, there is not one right answer for how to do the stationing, but the best answer is the one that is easiest to read while maintaining accuracy. Does that sound more or less correct?

I hope I am not oversimplifying but your stations should be laid out on a set increment and the additional stations added to show vertical, horizontal, or template changes. If you are not trying to actually create models and just produce a layout I would not add extra sections for intersections but just label where the CL of the intersecting road ties in.

I think there are too many variables to answer exactly. I'm not sure what the intended use of the plan is. 

 

[Dexman PE PMP]

Thanks both. This is not in an existing CAD program that CE's use, but rather an experimental feature yet to be released for another program. I cannot say what the program is until it gets released.

This starts to answer my admittedly vague question. (I assume that by '100+00+00' you meant '100+00.00', as you typed it in the 300 example.Correct)

So at the intersection you would show station points for all the involved roads? So for a 5-way intersection, you might have 3 station points (1 for each of the roads that 'continue through' and 1 for the road that dead ends)? Each road would have it's own stationing which is typically mutually exclusive of the other project elements. In your scenario of 5 roads, it would be likely that your assumption is correct, but I've also seen it so that each leg would have it's own resulting in 5 different stationing points.

And I gather this has nothing to do with the street names, and only relates to road hierarchies in as much as the designer chooses to incorporate them into their notations with the ultimate goal of producing a clear document. So in other words, in situations like these, there is not one right answer for how to do the stationing, but the best answer is the one that is easiest to read while maintaining accuracy. Does that sound more or less correct? Correct

Notes above in Red

Stationing layout is up to the designer.  Most try to follow some sort of logic (north to south, east to west, etc), but the logic isn't always clear to everyone. 

 

[LSF]

Cool, it makes sense to me now - especially after that last answer. Thank you both very much.

 

[LSF]

Hi again. This project went on hold but now it's back on. I thought writing here with the above context would be better than starting a new thread.

Some more stationing questions:

• I gather that the line (whether visible on drawings or not) on which the stations are placed is referred to as an 'alignment'. Correct? If so, is this fairly universal?
  
• Does this line always correspond with the centerline of the road?
  
• On a divided road, would you have two alignments, or one in the median? Or is it done in different ways depending on context?
  
• What if a road is undivided for a portion, then splits, then comes back together? (image attached)
  

Thank you!

 

[Ranger1316]

Hi again. This project went on hold but now it's back on. I thought writing here with the above context would be better than starting a new thread.

Some more stationing questions:

• I gather that the line (whether visible on drawings or not) on which the stations are placed is referred to as an 'alignment'. Correct? If so, is this fairly universal?
  
• Does this line always correspond with the centerline of the road?
  
• On a divided road, would you have two alignments, or one in the median? Or is it done in different ways depending on context?
  
• What if a road is undivided for a portion, then splits, then comes back together? (image attached)
  

Thank you!

1. Alignment can refer to horizontal or vertical but yes, usually the horizontal alignment with stationing is usually simply referred to as the alignment.

2. It does not always correspond to the centerline of the road. A lot will but this really depends on the project.

3. On a divided road, you typically have one centerline in the middle.

4. For a smaller, urban road like you have pictured, I would think there would only be one alignment. I had an interstate resurfacing job where the interstate split substantially and that had two alignments for each side that came back into one.

Let me know if you have any other questions

 

[LSF]

Extremely helpful. Many thanks.

 

[znjjay]

You should also consider where the crown of the road is and try to set the alignment as close as possible to that, especially when you have a major regrading of roads where you need to show a profile.  Coincidentally the crown is usually at the center of the road, that's why 80% of the time i try to find the middle between the face of curbs to set my alignment.

On a divided road that you showed with a median, usually the road will only slope to the right side, however at intersections the crown still exists, so it's best that the alignment be set in the center rather than 1 on each segment.