Civil 3D Intersection Design – Distorted Corridor Surface Due to Superelevation (-0.5% Slopes Before Intersection)

[17-ce-87]

Hello everyone,

I’m currently working on an intersection design in Civil 3D and encountered an issue with the corridor surface near the intersection.

Project Details:

• All approaching lanes must have a slope of -0.5%.

• Normal crown criteria:

  • Inside lanes = -2% slope

  • Outside lanes = -3% slope

• I have defined superelevation to manually control lane slopes for both primary and secondary roads.

Problem:

When creating a corridor surface, I notice irregularities and distortions near the intersection. I have tried:

• Adding top links as breaklines

• Adding feature lines for flange, flowline gutter, top of curb, and back of curb

However, the surface is still not smooth, particularly in the approach lanes.

Questions:

1. How can I maintain a smooth corridor surface when transitioning to a -0.5% slope before the intersection?

2. Are there best practices for superelevation transitions in short segments approaching intersections?

3. Could there be additional corridor settings or breakline techniques I should consider?

Any advice or examples from similar intersection designs in Civil 3D would be highly appreciated!
Thank you in advance.

[nkiakas]

Hi @17-ce-87 

Can you share your file to take a look?

Please also consider that the side slopes of the roads may vary in the junctions, to have smooth without "steps" asphalt surface in the junction.

I key tool for proper junction modeling is the connected alignment (of course together with the connected profile). Did you use this tool in your modeling?

Regards

[Joe-Bouza]

Why are we super elating on a straight?

for intersection design I would Rely on profiles to control cross slopes

[17-ce-87]

Please find the attached file for your reference.

Yes, I can relate with you regarding the importance of connected alignments. But the point is that, I didn't even design the intersection till now. 
The key problem is to achieve lane slope of - 0.5% as approaching the intersection. I've applied superelevation to achieve that target. Because of the rotation of lanes, the surface is getting distorted near the intersection.

NOTE: This intersection design is just for practice. If you find some design errors in the model, please guide me.

[nkiakas]

Hi @17-ce-87 

Do you want to maintain the crown in the primary road (South to North)?

I found out you created an alignment to maintain the crown

Regards

[17-ce-87]

Yes, the Primary Road crown must be maintained from South to North. Because the crown is shifting from the Left Lane # 1 ETW to the Mian Centerline Alignment of the Primary Road.

[Joe-Bouza]

Have you gone through any intersection tutorials? It doesn't look like it. Not to say it cant be done as you have it set up but you would be better off using the intersection paradigm. Looking at the drawing I guess you created a SE file in leu of a profile. It is and external file that reports and error when I try to look at targets on this end.

you don't need three corridors. one will get it done. the intersection object will give you the benefit and peace of mind that the profiles are locked where they need locking. 

traditionally, the return assembly is attached to the return alignment and targets the secondary and primary center line and eop for a maintain primary crown.

I suggest using the tutorials to better understand the process

[17-ce-87]

Hi Joe-Bouza,
I hope you're doing well.
Yes, I know the accuracy in the design by using the intersection paradigm, but as I mentioned before, I'm practicing an Advanced Intersection Design by starting from the scratch. Traditional Method is helping me a lot to understand why these issues are occurring and what could be the possible solutions for them. I think it's better for me to tackle these issues by finding logical solutions instead of avoiding them.
FYI, I'm following Jeff Bartels Playlist for this intersection design.
Civil 3D Advanced Intersection Modeling 

[Joe-Bouza]

I'm not suggesting you avoid. The intersections tools allows you to choose the alignments and profiles that you defined.

I check out the link.

Thanks

[Joe-Bouza]

Ok, that's legit. where did he assign the SE to the primary and secondary? I saw him set the subs to SE but never saw him assign SE to the alignment. 

[Joe-Bouza]

CONTOURS AFTER SMOOTHING