Evaluation of alternative intersection treatments at rural crossroads using simulation software

Objective: Rural roads are characterised by hazardous roadsides and suboptimal geometry, yet allow for high travel speeds and unfavourable impact angles. In Victoria, 25% of persons seriously injured and 52% of fatalities occur on rural roads, with 30% occurring at intersections (Transport Accident Commision, 2016; Victorian Parliament Road Safety Committee 2002). In the USA, almost twice the number of traffic fatalities occur in rural areas than in urban areas, whilst accounting for less than half of all vehicle miles travelled and 21% of the population (NHTSA 2002). The choice of safety countermeasure is therefore paramount. Simulation software provides a cost-effective means of analysing alternative intersection treatments with a view to identifying their effectiveness in mitigating crashes. The aim of this research was to assess the safety benefits of four alternative intersection treatments using in-depth crash data with an advanced crash reconstruction process. Method: Using a single serious injury real-world crash from the MUARC Enhanced Crash Investigation Study (ECIS, Fitzharris et al., 2015) and crash reconstruction software, an exemplar rural crash was reconstructed and validated against real-world data. The crash involved a passenger vehicle (EuroNCAP 5*) approaching from a minor road and failing to yield at a ‘give-way’ sign; the posted speed limit was 80 km/h. The vehicle was struck on the right/driver side by a rigid truck (B-vehicle; 1990) travelling on the major approach (100 km/h). The driver of the case vehicle was seriously injured. Four alternative intersection treatments appropriate for the crash site were constructed in CAD software (Rhinoceros V5): roundabout; rumble strips; a reduced speed limit and the combination of lower speed limit and rumbles to determine the reduction in crash forces in the presence of the countermeasures. Results: The hypothetical scenarios demonstrate substantial reductions in impact force and different points of impact, resulting in a significantly lower injury severity for the struck driver. Speed limit reduction to 80 km/h on the main approach (from 100 km/h) in combination with rumble strips on both intersection approaches had the most favorable outcome with the crash avoided entirely, assuming speed compliance. Discussion: The findings have implications for understanding the role of speed in crashes, and hence the design of effective countermeasures. Simulation software, validated using real-world data, provides a cost effective means of evaluating alternative intersection treatments for rural intersections. Scaled up, implementing these treatments would have significant safety benefits and reduce the road trauma currently associated with rural roads.