Research on working widths for concrete road safety barriers has just been released to provide clearer guidance on safer infrastructure and roadside design across Australia and New Zealand.
The working width refers to the space that is required behind the concrete barrier to accommodate the movement of a vehicle or barrier system during and after an impact. It is critical to get this right, according to Austroads, to prevent secondary collisions with roadside hazards – particularly if heavy vehicles are involved.
The research establishes revised recommended working widths for test levels TL‑3, TL‑4, and TL‑5 concrete barriers, with values varying according to barrier height and containment level, Austroads revealed.
These recommendations account for the behaviour of heavy vehicles during impacts and include adjustments to reflect Australia’s maximum legal vehicle height. The research report also discusses the implications of working width selection in tunnels and lower speed environments, where vehicle behaviour and impact conditions differ from open road settings.
According to Austroads, while working widths may be influenced by these conditions, the research reinforces the importance of understanding the underlying principles of vehicle intrusion and barrier performance when applying the guidance.
Michael Nieuwesteeg, Austroads Road Safety & Design Program Manager, explained that concrete barriers on bridges, in tunnels, and on high-speed corridors are highly constrained environments where there is limited tolerance for error.
“This work gives agencies and designers a more robust technical basis for determining how much space is required behind a barrier to manage heavy vehicle impacts safely,” he said.
The study draws on zone of intrusion data developed under the Manual for Assessing Safety Hardware (MASH) testing framework, which reflects how vehicles interact with rigid barriers under modern impact conditions.
While existing working width values used by road agencies were found to be generally consistent across jurisdictions, Austroads said the research re‑evaluated these values using evidence from international crash tests and computer simulations that examined how far vehicles moved behind concrete barriers during a crash.
Austroads stated that the findings and recommendations from the research are expected to inform future updates to its Guide to Road Design Part 6: Roadside Design, Safety and Barriers.
You can read more about this in Austroads’ Working Widths for Concrete Barriers, which is available to read for free.
About the author
Desi Corbett
Desi is the Editor of Concrete in Australia, at the helm since December 2013, and our weekly news writer since 2016. Focused on concrete and construction for more than 11 years, her expertise in this field forms part of a journalism career spanning three decades. To get in touch please email desi@corbettcomms.com