This report details research carried out in Wellington, New Zealand, over the period 2012–13. The broad aim was to develop relationships between rut depths and crashes on New Zealand's state highway network.
A literature review suggested that deep ruts could either:
A method of predicting pond depth on New Zealand's state highway network using New Zealand databases was developed. Comparisons of predicted flow path length with measured data were encouraging.
Key findings of statistical studies of the relationship between crash rates and rutting on New Zealand's state highways were:
Due in part to the paucity of ruts in the 10–30mm range, statistically robust benefit-cost ratio estimates could not be calculated. However, for shallow ruts, the statistical modelling indicated that filling could not generally be justified.