Design and Construction of Low-Cost, Low-Volume Roads in Australia

Inexpensive roads constructed by using local knowledge of material behavior have been shown to be capable of meeting rural traffic requirements without the need for importation of hard and expensive quarried crushed rock or gravel. In Australia, low-cost, low-volume roads are typically rural roads constructed in a broad range of operating environments, varying from arid to tropical. The areas that contain the longest length of rural roads, however, are arid or semiarid and are often subjected to periods with low levels of precipitation and high levels of evaporation, frequently followed by periods of intense rainfall. Locally available materials for road making may not meet the usual standard road authority requirements for high-quality aggregate and are thus termed "marginal," "nonstandard," or even "inferior." Because these materials are a resource that cannot be ignored, locally derived specifications are formulated for specific materials to allow more efficient expansion and maintenance of road networks in remote rural areas. Many of the subgrades within arid and semiarid areas are sensitive to water ingress and are termed "cracking" or "expansive" clays. The combination of hostile environment, poor subgrade, and marginal construction aggregates means that the engineer must take an entrepreneurial approach when developing the rural road infrastructure. Some of the methods used to develop and maintain a highway infrastructure for remote rural areas in Australia are outlined, with the Western Queensland region used for illustrative purposes.