Hydraulic conductivity is an important material parameter for pavement engineers. The ability to make a priori estimates of the coefficient of permeability of road pavement materials is very useful when studying issues of pavement durability and predicting pavement performance. This paper presents two laboratory databases assembled from data sourced from the literature. Using a database of permeability tests on fine-grained soils, the ability of the Kozeny-Carman void ratio function to

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... the data is examined alongside a simple power-law relationship. A second database of permeability measurements on asphalt concrete specimens is used to re-examine the 'representative pore size' concept as a method of predicting the coefficient of permeability. The influence of nominal maximum aggregate size (NMAS) on the coefficient of permeability is also studied.