The majority of fatal and serious crashes in New Zealand occur on rural two-lane roads. Data on historic crash patterns is not always sufficient to enable a suitable diagnosis of the safety deficiencies of various sections of this rural road network. It also cannot readily identify safety issues on low-volume roads and shorter sections of highway, where the relative scarcity of crashes may mask the considerable potential for proactive safety improvements.
This report presents the third and final stage of a study that aims to develop crash prediction models for two-lane rural roads using data from almost 7000km of the rural state highway network. The report builds upon the findings of stage 1 (scoping study) and stage 2 (pilot study) to determine the most important parameters affecting safety on rural roads in New Zealand. The models have quantified the mathematical relationship between crashes and traffic volumes, road geometry, cross-section, road surfacing, roadside hazards and driveway density. These crash prediction models have enabled a better understanding of how safety is impacted by these factors and allow an understanding of how they interact with each other. They can also be used to determine which improvements are best to reduce crashes, for example whether to realign a road, widen the shoulder or remove roadside hazards.