Monty Diet: How to help the Montague Street Bridge eat less trucks

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Years of vehicle hits – It’s time to look differently. 

Proposal to reduce over-height vehicle collisions with low bridges in Melbourne CBD

18 January 2021

The incidence of vehicle collisions with several central Melbourne bridges has become so commonplace that at least one bridge has its own Facebook page. Each collision results in half a day of productivity loss to Melbourne. Traffic is diverted, train lines to Flinders Street are stopped, emergency services are called to the scene and engineering crews are sent out for safety checks. The question every Melburnian has discussed over the years is why drivers keep attempting to drive under bridges that are too low for their vehicles.

There are clearly multiple factors that have caused these accidents. The accidents range from minor annoyances to major collisions causing injury and severe distress, and a bus driver was jailed on charges of negligently causing severe injury. There have been near as many attempted solutions to the problem as there have been incidents.

While each of these warning-based solutions has doubtless helped the situation, drivers are still hitting bridges, regularly.

It’s the railway bridges that get hit

One aspect that has been overlooked thus far is to consider how the bridge itself is seen by the driver and why they are not more cautious in their approach and naturally consider the hazard ahead.

The warning signs and bump bars currently in place are not enough to solve the problem so we suggest that the bridge itself needs to be made more obvious, both the entrance and the internal space. In doing this, we are proposing a psychological solution rather than an engineering solution to the problem. In using the science of vision and depth perception we are able to affect the behaviour of drivers.

Whites illusion
Figure 1: White’s Illusion

shows how A and B are the same shade of grey but look different against light or dark.

Image source: By Zhengyi4411 – Own work, CC BY-SA 3.0,

One of the consistent characteristics of the bridges is that they are original railway structures that are internally quite dark and have an internal roof space higher than the entrance or the beams. The rail tracks going each way further leave an open light space in its centre line. People perceive height from the average of light and dark queues. Inconsistent lightness leads people to believe space is bigger than it is.

The suggestion we wish to test is that this structure of Melbourne’s collision bridges makes the appearance seem less restricted in height than it is and that we could address this quite simply by using white paint and boarding to brighten the internal space and give a consistent ceiling height.

In addition to making the internal space more visible from the approach we also would like to test whether changing the entrance to the bridge would have an effect. The use of warning stripes and text has not had the desired effect, possibly because we are so desensitised to such things. Drivers’ behaviour has not been affected by the warnings in place and an innovative approach is needed.

Instead, we suggest the use of street art to highlight and draw attention to the bridge entrance as an alternative. Normally drawing attention away from the road while driving is not a good thing, but in this circumstance, the static street art becomes a vision perception queue. This approach would illustrate the restricted height of the bridge in an innovative way, look more attractive than it currently does, and be easy to update and maintain novelty and relevance. Furthermore, it involves the community in the solution. This can easily be done on a single bridge to test the validity of our proposal.

We propose the City of Melbourne and the City of Port Phillip undertake a world-first trial in Spring 2021 using the science of psychology to solve a hundred-year-old problem.


Lauren Sherson

Lauren Sherson was a student in Melbourne University’s Graduate Diploma in Psychology. She has a background in innovation and how it can be used to solve complex problems.

Simon Cropper

Simon Cropper is a vision and perception scientist. He also created Melbourne University’s Graduate Diploma in Psychology. Simon investigates psychological solutions that enhance the human experience.

If was after one of Simon Cropper’s lecture in vision and perception psychology that Lauren asked if the subject theory would explain why vehicles keep driving into the Montague Street Bridge. An investigation together down in South Melbourne led to the short answer – yes.

Shoghi, A. (2019, April 1-2). Using intelligent transport system strategy to prevent/reduce over height vehicles from striking the Napier Street Railway bridge. 9th Australian Small Bridges Conference 2019. Surfers Paradise, QLD, Australia. 

(c) Lauren Sherson & Dr. Simon Cropper 2021

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