This project sought to identify areas of improvement which would bring safety performance of selected Safe System infrastructure elements closer to the vision’s objectives. The report summarises the key aspects of Safe System performance for signalised intersections, roundabouts, and wire rope barriers in wide-median, narrow-median and roadside applications. It then documents findings of literature, statistical analysis of site data and in-depth severe crash analysis to identify factors contributing to their occurrence at these infrastructure elements. Further literature and expert inputs helped to identify suggested solutions to address these factors and to provide broad guidance for consideration in future Austroads guide revisions. In the process, the project proposed a new approach to definition of what constitutes road infrastructure aligned with Safe System objectives. Further, the project proposed fundamental relationships between impact speed and probability of fatal and serious injury, based on recent US research. For signalised intersections, the leading severe crash factors were high entry speeds and unfavourable impact angles (e.g. right-angle, head-on), followed by red-light running, lack of full right turn control, large size of site (multilane, high number of conflict points), inadequate signal visibility, and high pedestrian activity. The suggested solutions align the signalised intersection form closer to the Safe System ideal, and include signalised roundabouts, horizontal and vertical deflections on entry. A number of treatments were identified as supportive to any or all of these solutions e.g. movement control and management, lower speed limits, and red light/speed cameras. For roundabouts, the focus was on improving safety performance for cyclists and motorcyclists. The key severe crash factors were related to high speed approach and entry into the roundabout, and included multiple approach and circulating lanes, or lack of effective approach deflection. Project stakeholders also identified high speed exit conditions as a potentially contributing factor in injury crashes. Confusing layout was also a factor leading to drivers not seeing, reacting and giving way to the two-wheelers. The proposed Safe System solutions included reduction in approach and entry speeds such as tighter geometric design and raised stop lines/platforms. Identified supporting measures included arterial traffic calming, cyclist bypasses, and signalising roundabouts. Wire rope barriers generally deliver substantial safety improvement for most road users compared to other roadside design options. It is proposed that further research and development of guidance focuses on refinement based on application of optimal wire rope barrier systems for different locations, so that risk of severe injury outcome is minimised. Consideration of barrier system stiffness appears to be one area for further investigation. The report also noted a number of additional areas of interest in future wire rope barrier research. (Author/publisher)
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