Intersection Design Y-Junction 3- centered semi arc. C3D 2023 vs Inroads Bentley Rail Track

[Solodaeth]

Dear forum,
I am working on Y junction with 90 degree and 60 degree turn angles asper AASHTO green book on C3D 2023. I have also worked the same on Inroads with limited proficiency despite the flexibility I noticed to design intersection on Inroads. However, unlike Inroads C3D doesn't have data field to insert symmetric offset value while designing asper AASHTO. For instance, for design vehicle WB-19 with angle of turn 90 degree- 120m-21m-120m; three centered semi arc with 3m symmetric offset, Inroads will allow you to insert the above parameters specifically symmetric offset which I am highly interested.

On the other hand, C3D will allow you to create 3 centered semi arc with 120-21-120 and curve length but without symmetric offset value. Can anyone tell me how to fix this issue ?. How to Co-relate AASHTO with C3D to insert symmetric offset and to create turning road way alignment/fillet as Inroads. How to determine the curve length?
As general thumb rule, I am adding 2x symmetric offset value shown on AASHTO table to the middle curve radius I.e ( 21m + 2x3m) to get curve length so that the turning road way alignment will resemble Inroads output. For your easy reference, I have attached AASTO table, my Y- Junction layout and Inroads junction creation window.

kindly regards,

[Cadguru42 · Accepted solution]

I'm not sure exactly what you're asking. If the design criteria aren't able to do what you want, then just draw the layout the way you want and use it as targets for the corridor.

[Solodaeth]

How do you create Curb return alignment in C3D. as per AASHTO please refer the image attached below. Symmetric offset? how do you know the curve length to create 3 centered arcs. However, Inroads software you will have room to insert data (symmetric offset)  as per AASHTO table to create edge of travel way at intersection you dont need to worry about curve length.

[Cadguru42]

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@Solodaeth wrote:

How do you create Curb return alignment in C3D. as per AASHTO please refer the image attached below. Symmetric offset? how do you know the curve length to create 3 centered arcs. However, Inroads software you will have room to insert data (symmetric offset)  as per AASHTO table to create edge of travel way at intersection you dont need to worry about curve length.

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It sounds like you might need to understand what the tables actually mean and not rely completely on the software to do the design for you. With that said, below is how I'd go about doing it.

1. Offset the two typical EOTs to your 3m offset.
2. Fillet the two offsets by 21m that the table says.
3.  Create another 120m fillet tangent to the 21m arc and the typical EOT.
4. Trim
5. Repeat for the other side.

[Solodaeth]

Thank for your swift replay. I don't opt manual operation. I would rather want automatic creation. I believe that it can be managed on C3D.