The Impact of various maintenance strategies on unsealed road deterioration to achieve an acceptable maintenance budget & road performance
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In Australia unsealed roads comprise nearly 60% of the total road network length. These roads play a vital role in providing agricultural, mining and tourist access across Australia. In the Northern Territory of Australia unsealed roads comprise over 70% of the total road length. ARRB has been involved in developing maintenance strategies for the unsealed road network in the Northern Territory to establish a long-term stable maintenance budget that provides a sustainable unsealed road network for all the road users. The initial basis for the analysis and estimation of the maintenance budget were the road deterioration (RD) models derived from the local roads deterioration study (LRDS) that was conducted over a 10 year period across Australia. Further refinement of these RD models and the development of Australian based works effects (WE) models was provided by a two year study of the performance of a large sample of unsealed local roads aimed at quantifying the immediate and longer term impact of grader blading and its frequency on the deterioration and surface re-sheeting on unsealed roads. Various maintenance strategies were tested using different grader blading intervals and varying the extent of the blading across the pavements in conjunction with drainage works and the ultimate replacement of the surface materials. Using this approach maintenance strategies were found that provided an acceptable annual maintenance budget in combination with an acceptable range of rideability and pavement crossfall. The long term performance modeling of unsealed roads was trialed in the Northern Territory. Whilst the models rely on treatment (grading) frequency, modeling of several treatments within a year required a novel approach. This approach is presented in detail, together with the results on the budget and maintenance strategy development.