Relationship between Traffic Loading and Environmental Factors and Low-Volume Road Deterioration

Many countries use some form of model to determine road user charges. Trucks are expected to pay for most of the cost because heavy vehicles are responsible for most of the deterioration of roads. This research documents findings that will ultimately be used to refine the New Zealand road user charge models. The research was undertaken on data from the Long-Term Pavement Performance Program with the specific aim of determining the relative damage caused by heavy-vehicle loading alone compared with the combined effects of loading and environmental impacts. As part of the overall research process, a cluster analysis was undertaken. The results from this analysis also emphasized the importance of drainage. The cluster analysis resulted in a recommended stratification of low-volume roads on the basis of their urban or rural location, traffic loading, and climatic area. This stratification could be used for a more detailed implementation of a user charge model if needed. On similar low-volume roads, an approximate 0.1-mm/year higher rut rate was observed in areas that had a wetter climate in combination with sensitive in situ soil conditions. The results also illustrated that adequate drainage was vital for limiting environmental impacts. Roads with inadequate drainage had a rut rate 2.5 times as high as that of roads with the necessary provision for drainage.