Restricted Environment Motorway/Interchange Design
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.
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
The team also had the problem of how to present the solution to a
layperson simply and quickly.
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 team was able to present the client with output from their analysis using
the drive-through functionality in 12d Model, which
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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
—George Eivers, Traffic Design Group