Restricted Environment Motorway/Interchange Design - Traffic Design Group

ClientTraffic Design GroupLocationNew Zealand
ConsultantTraffic Design GroupContractorGeorge Eivers

Restricted Environment Motorway/Interchange Design

Project Summary

Traffic Design Group was given the job of assessing whether a 1.6km long motorway and associated interchange could be designed to avoid specific horizontal and vertical restrictions.

An existing road required upgrading to motorway standard, including an interchange, following the placement of other infrastructure. The motorway needed to be able to circumvent future developments and pass under an aviation flight path, while still meeting design standards. 12d Model software was selected for this task.

The Challenge

In order to establish a feasible alignment, the design needed to take into account the curve radii as well as design speed to determine super elevation. Applying super elevation modified the vertical alignment and required transition curves, which modified the horizontal alignment.
This resulted in an iterative design process, which would have been very time consuming to work with.
The team also had the problem of how to present the solution to a layperson simply and quickly.

The Solution

Using super alignments and the Apply Many function, they added each road and structure to the model in 12d.
When adding the motorway, they input the super elevation and transition curve information; often this would mean the ‘horizontal geometry is not solved’, but by simply moving the curve apex a satisfactory alignment could be quickly and easily be established. This relatively fundamental aspect of 12d Model proved invaluable in quickly generating geometrically correct options.

The Result

The team was able to present the client with output from their analysis using the drive-through functionality in 12d Model, which
“...was invaluable. Without an aerial to drape, the sky dome seemed out of place thus we shaded the tin and extruded roadmarking onto the new alignment to simulate the preferred option.”
—George Eivers, Traffic Design Group

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