An almost essential part of modern life-cycle road asset management is the ability to predict future performance. This paper identifies models for a range of unsealed road properties from published research papers. Those selected are considered appropriate for New Zealand conditions. Because they are so varied and change from day to day, performance prediction for unsealed roads is difficult: hence a probabilistic rather than a deterministic approach is preferred. Roughness is the favoured basic performance predictor for all road types. It is almost universal for sealed roads. Using it for unsealed roads provides a similar basis allowing compatible estimation of both road user and road provider costs. Nevertheless for good management of unsealed roads other predictors are required including ones for grading frequency and aggregate replacement. It is concluded that even the best predictors need local calibration and that more reliable results are obtained by pavements which have been constructed and maintained in accordance with `good practice'. (A)
Samenvatting