Road / Rail Geometry Combined vertical and horizontal curves

I need to draw roads and railways including bridges and tunnels. The geometry is based on horizontal and vertical curves being applied to the same straight line but starting and finishing in different locations.
This is a common problem for all civil engineers and I hope by now Sketchup can offer a solution. I raised this issue in Aug 15 but have still not found a solution.

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At first take this seems doable in Sketchup. But it seems like it was doable back in sketchup 15 as well, so perhaps I’m missing something. Can you describe what goes wrong when you try this? Or post a screen shot or better yet a sketchup file with the problem illustrated?

Dear Riley,

Thanks for your offer.

I cannot post a screen shot as I cannot make it happen.

Road and track horizontal geometry is based on a series of straight lines which meet at intersection points.

Horizontal curves are then applied between straights with radius depending on design speed and space available.

Vertical curves are applied in the same way with fixed gradients (up or down) meeting at vertical intersections where again vertical curves are applied.

One issue is that the start and finish of horizontal curves has no matching relationship with the start and finish of vertical curves.

The first problem is how to take a straight line on a horizontal plane and apply a curve to it, then apply a curve in the vertical plane to the same curved line.

I don’t think SketchUp can cope with this but it is such a basic tool for designers of roads and railways that it would be very helpful if this facility was available.

I did get offers of help in 2015 but none successful so I thought I would try again.

Kind regards


Are you talking about something like this?


Is this the design concept you are referring to?

Hi Box,

Yes this looks just what I need.

Many thanks


Hi Chris,

Yes that is the idea but we can use circular curves for simplicity in generating design models.

The target is to model a motorway interchange showing how all the ramps and viaducts fit together in the space available.

It is not just a question of joining a horizontal curve and a vertical curve into one shape. You actually have to apply the vertical curve to the curved plane of the horizontal curve so that the lengths of each curve remain correct in curved planes.

There is software for this but I was hoping to manage it in Sketchup to save money.



Can you show any images or drawings of the issues and results you are looking for?

Look at this thread for Inspiration also search Daniel Tal SketchUp Base Camp videos

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