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Crash performance of safety barriers on high-speed roads.
The findings presented in this paper are based on Austroads funded investigations of the in-service effectiveness of safety barriers on high-speed roads (that is, roads with 100 and 110 km/h speed limits). Based on past evaluations, the most promising was continuous application of flexible barriers on freeways addressing up to 86% of run-off-road and cross-median casualty crashes. Analysis of Victorian barrier crash data from high-speed roads suggested that the severity index for run-off-road casualty crashes (FSI ratio) was 0.58 for semi-rigid barrier crashes compared with 0.75 for tree crashes. Severity of run-off-road casualty crashes into semi-rigid barriers was comparable to those not involving a roadside hazard (FSI ratio of 0.55). In contrast, flexible barriers had the lowest FSI ratio of 0.38. Continuous flexible barriers appeared to be the most effective safety barrier solution among those reviewed.
Investigation of the effect of semi-rigid barrier offset from the edge line showed that the FSI ratio increased at a low rate with increasing barrier offset (~0.03, or 5% per m), although the relationship was not statistically robust. Combined with earlier research on barrier crash likelihood, the suggested ideal range for barrier installation could be in the range of 1.5 to 4 metres to allow for sealed shoulder provision. These findings may be useful in refinement of barrier selection and design guidance.