The Author sets out the criteria for filter material and refers briefly to the physical characteristics of permeability and capillarity. A recommended type of design for the subsoil drainage of roads and aerodrome pavings is descriptionbed and other uses of filter material are mentioned. Examples of good and bad practice in subsoil drainage are given.
Standard methods of soil survey and design of road are descriptionbed in detail in publications readily available to all who are interested. This paper deals only with those aspects of soil survey and design of roads which are not generally commented on in these publications.