2004 - Australia - Roughness Deterioration of Bitumen Pavements

Pavement engineers have used road roughness as an indicator of a road’s functional performance for many years now. Generally, the roughness data has been viewed in terms of a pavement’s current absolute condition in which excessively rough roads will be earmarked for further engineering investigation and possible remedial works. Engineers have also attempted to predict the future roughness of their road network so that appropriate funding can be proactively assigned to maintain an acceptable level of service for road users. To undertake these future predictions a roughness progression model, or deterioration model, is used to increase the roughness of the pavement in proportion to its age and other parameters. Many deterioration models are available, however anecdotal evidence from practitioners indicated that the theoretical roughness progression provided by many models is rarely mimicked in real life. As such, a research project partnership was established between the Queensland Department of Main Roads and the Queensland University of Technology to investigate road roughness progression.

This paper outlines the research effort undertaken in 2001 that reviewed the actual time-series roughness progression of approximately 16,000 individual pavement segments, each 1km in length. The research was undertaken using data from the Queensland Department of Main Roads’ database and spans between 4 and 14 years of roughness information. The technical challenges and resulting methodology of analysis of the time-series roughness data is discussed. The research also investigated the effects of pavement maintenance and reviewed many of the common variables such as age, soil type etc that are used in roughness prediction models.

In 2003, the analysis was re-performed with three years of additional roughness data and revealed similar results to the 2001 research. Currently the Australian Road Research Board is investigating the use of roughness progression to assist in identifying under-performing pavements. Further improvements on the current methodology and future uses of actual pavement roughness progression are also discussed.