PUSHING THE BOUNDARIES OF ROAD SAFETY RISK ANALYSIS

In order to address the safety and efficiency issues out on the transport network, traffic and road safety engineers often come up with innovative design solutions. The safety of such schemes can be difficult to assess given that most of the safety research has been developed for standard intersections. For example in the Economic Evaluation Manual: Appendix A6 crash prediction models and crash reduction factors are provided for standard intersections and road links and common treatment types. There are also limited models around that can assess the risk of serious and fatal crashes. This paper discusses three studies that have considered non-standard intersection and rural road upgrades/treatments in the Bay of Plenty. The first two include a signalised roundabout at the Takitimu/Elizabeth Street and Te Maunga (SH29)/Tauranga Eastern Link (TEL) intersections and also a displaced right turn signalised T-junction at the latter intersection. Crash prediction models and overseas research have been used to assess the relative safety of these alternative intersection designs. These have also been compared with standard intersection configurations. For intersections the risk of serious and fatal crashes is assessed using various research on severity including factors provided in the High Risk Intersection Guide. Specific research on crash rates and crash severity were also used to look at combination of clear-zones and barriers on the shoulder of the TEL and the effect on the risk of serious and fatal crashes.