Research & reports
New Zealand granular pavement design is currently based on the assumption that all deformation of the pavement shape under traffic loading occurs in the subgrade. To reflect this theoretical behaviour the AUSTROADS document Pavement design – a guide to structural design of road pavements (AUSTROADS 1992) is based on limiting the vertical strain on the subgrade. AUSTROADS (1992) was adopted as a design methodology by New Zealand in 1996. In 2004 a newer version of the AUSTROADS guide was issued (AUSTROADS, 2004a) and this document is now the current pavement design guide in New Zealand. Just as with the 1992 document AUSTROADS (2004a) continues with the design methodology of minimising the subgrade strain according to the design traffic. This study, initiated in 2004, examines the design methodologies presented in AUSTROADS and evaluates them against available New Zealand research. Various subgrade strain criteria are examined for New Zealand conditions.