High inflation in road construction and rehabilitation costs, particularly in the area of haulage, has caused the New Zealand National Roads Board, through its Road Research Unit, to look for economies. One solution has been to use lime as an additive to base aggregates that would not normally comply with the demanding specification for this material. In some instances this could mean using a substandard base aggregate from a local quarry instead of an up-to-standard material hauled from a quarry farther away. In others, it could mean adding lime to the in situ recycling of a badly degraded base instead of using a granular overlay that has implied higher haulage costs. A description is give of the application of varying proportions of lime to a very substandard base aggregate, its testing in the laboratory, and full-scale field trials carried out at the University of Canterbury's test track at Christchurch. The field trials revealed that a substantial improvement in performance was obtained by adding 4 percent hydrated lime. This figure was predicted in the laboratory by the pH test, unconfined compression, double-punch tensile test, and the California Bearing Ratio. It is concluded that all these tests indicate the right concentration of lime, but it is not suggested that any one, on its own is sufficient owing to the complex mechanisms at work in a road pavement.