The satellite view of this overpass (on Google Maps) shows some banded earthworks.
When driving by, you can see that each band is an elongated triangular shape (street view):
My guess is that these earthworks act as a wind break by making the wind turbulent, so as to minimise the force of cross winds on the overpass.
Is that what they're for? What are they called?
Visually appealing, natural shaped barriers to decrease noise and light from a heavy use freeway.
From: Peninsula Link - Information Sheet
The landscape design also includes major shaped earth features, sometimes known as land-forming, at the Bungower Road and the Mornington-Tyabb Road interchanges.
Along with providing interesting visual features along the roadway these land forms also act as natural barriers to light and sound.
The view from Mornington-Tyabb access ramp at is more representative of the actual barrier.
From Penisula Link - Managing road traffic noise
Managing traffic noise on the freeway is a key aspect of the Peninsula Link design.
Where the acoustic model for Peninsula Link predicts that the noise limits in this policy are likely to be exceeded, noise mitigation measures such as noise walls and earth mounds will be applied to reduce traffic noise.
The choice of noise mitigation measure depends on the space available, aesthetics, visual impact and the practicality of building noise walls within the road reserve.
The height and location of the noise walls and earth mounds on Peninsula Link have been determined using the acoustic model.
They had space available, so they used shaped earth mounds to block noise and light from the expressway from the surrounding countryside. Better than unsightly noise walls.
View from Bungower overpass from 2013 showing tent-like structure of earth-works. They clearly tower over freeway blocking view and sound of freeway from access roads (and surrounding countryside).
The earth mounds appear to be all the same shape, same angles, same peak to peak distance, parallel to intersecting road, with increasing number of planted trees off of mound peak. They are seeded with ground cover, no trees or bushes. Both intersecting roads are overpasses, which would cause amplification of sound as vehicles pass underneath.
This is too specific. If you take what they say as guidance. They ran acoustic models of noise levels that would be produced and this is the solution to cancel out the prominent frequencies that would be produced by traffic.
A noise wall is just a noise wall. They have used them all over the expressway in residential areas. Mounds shaped as triangles is unique. They even have an artistic rendition of the Bungower mounds. This is some highway engineer's pride and joy. Something they can show their grand-kids. Their signature.
It would be easier to flatten out the land and plant trees. That would block noise and visual impacts. This is used of other areas of the road.
