Expanded operating speed model

Austroads Project TS1456 Expanded Operating Speed Model was established to update and expand the road design operating speed models used in Australia. In particular, the project reviewed the validity of the existing operating speed model for rural roads and identified adjustments to the model that reflected changes in driver speed behaviour. This included the deceleration of cars and heavy vehicles on horizontal curves and the influence of horizontal curves in sequence. The existing Austroads operating speed model for rural roads was adopted in the early 1980s and validated in the 1990s with no further refinement or developments in later years. This project provided an opportunity to apply newer data collection methods and technologies such as in-vehicle and point-based speed measurement, application of network survey vehicle data and methods of location matching. It also considered whether vehicular operating characteristics had changed since development of the existing model. The project developed a process to collect and analyse speed data on horizontal curves and assess the implications in terms of the deceleration on horizontal curves for cars and trucks and the influence of curves in sequence. This was used to develop potential revisions to the Austroads operating speed model. This paper provides an overview of this project, the methods of data collection and analysis, the operating speed model developed, further research and implications that the project may have for the Austroads Guide to Road Design.