Development of an Alternative Design for Single Slope Concrete Barriers to Reduce Working Width

In the most recent 2020 edition of the Austroads Guide to Road Design Part 6, important amendments were made to the required working width values for public domain extruded concrete road safety barriers. These changes deviated from the narrower widths that some Australian states, particularly Queensland, had adhered to for decades. During the transition, many completed road designs followed the previous standards for concrete barrier working width, raising concerns among asset owners about whether the residual risk is acceptable – especially when the barrier shields bridge piers or other critical roadside structures. The catastrophic risk of bridge collapse could result in serious injury or even fatality among other road users. To address this challenge, two extrapolation methods were developed based on the only available crash testing for a single slope concrete barrier. These methods retain the profile of the public domain single slope concrete barrier commonly used in Queensland but achieve a reduced working width by increasing the barrier height. Practitioners would benefit from this evidence-based approach when the existing or designed cross-section is constrained and the structure is at risk of impact. The relevant design guidance and considerations have been discussed to establish the conditions for use. The outcome of this study has been summarised in a technical note published by the Queensland Department of Transport and Main Roads for practitioners to consider under the domain of Design Exception.