Barriers should be installed between 1.5 m and 4 m from the road shoulder. At the time of writing of this report, work under way for Austroads project ST1427 demonstrates that barriers placed any closer to the roadway lead to a significant increase in collisions with the barrier. However, as the barrier’s offset is moved further from the roadway, the impact angle increases, resulting in increased crash severity. This research prescribes a maximum four metre offset before the proportion of fatal and severe crash outcomes becomes too severe.