Using the Austroads operating speed model (maybe we will get it right this time

Historically, roads have been designed to meet some appropriate standard by assuming a design speed for a significant length of the road. Australian research in the late 1970's found that where a design speed less than 100km/h had been assumed, the actual operating speeds were very different from the assumed design speed. This phenomenon was also found in other countries. However, what set Australia apart was that the Australian research also produced a speed prediction model (the speed-environment model) that allowed the design of the road to match how it ended up being driven. Unfortunately, the speed environment model was poorly implemented throughout Australia. One solution to this was the development by VicRoads of the operating-speed model. It was adopted by Austroads for the 2003 edition of the Geometric Design Guide of Rural Roads. This paper: 1. covers experience with the operating-speed model within the Queensland Department of Main Roads for more than 4 years – including a simple enhancement that retains a key property of the speed-environment model; 2. explains the advantages over the speed-environment model for practitioners; 3. explores the likelihood of how well it will be taken up and recommends practices to help ensure that this happens.