A two-year study was completed in 2016 in conjunction with Cassowary Coast Regional Council (CCRC) in Queensland and Blayney Shire Council (BSC) in New South Wales to measure the performance of a sample of unsealed local roads in their networks. The aim was to quantify the immediate and longer-term maintenance impact of grader blading and surface re-sheeting on unsealed roads. The study followed earlier work at Moorabool Shire Council (MSC) conducted in central Victoria from 2012 to 2014. In 2015-16 measurement of the base-line rideability (road roughness) condition, using a roughometer, commenced on survey sections in the BSC network. The survey sections were selected in the BSC network based on planned maintenance works and regular measurements of roughness. Roughness was measured before and after the maintenance works along with quantification of other variables influencing pavement performance including traffic. Prior to the study, CCRC had collected extensive roughness measurements across its whole unsealed road network in 2014 and had captured the impact of maintenance on designated sections. The study, using the CCRC, BSC and MSC survey sections, involved data assembly, performance analysis and documentation of the resulting refined models from the roughness data collected to improve the existing unsealed roads road deterioration (RD) and works effects (WE) models. The following outcomes were achieved: *Statistically significant WE models were developed for light blading, medium blading and granular resheeting maintenance works. * The WE models are typically a function of the roughness before maintenance (IRIb), the timing of the roughness measurements before and after maintenance (NDay) and annual precipitation (AP). Traffic was not found to be a statistically significant variable in most of the WE modelling. * The WE models for the medium blading and re-sheeting predicted similar impacts on the roughness before maintenance (IRIb) despite the differences in maintenance effort. This outcome was contrary to the earlier findings at MSC. However, the longer-term impact of the different maintenance activities was not observed on road deterioration. * A statistically significant RD model was developed for roughness deterioration between maintenance activities. * The RD roughness deterioration model is a major function of annual precipitation (AP), time (TG2, TG1) and the roughness before maintenance (IRIb). Traffic was also not found to be a statistically significant variable in the RD model which may be a characteristic of the three road agencies in the study. * The RD model is a simplified form of the roughness deterioration model from the previous Local Roads Deterioration Study (LRDS) work and does not require assignment of a maximum roughness (IRImax). The above WE and RD models may be able to be adapted for other road agencies provided they are calibrated against measured performance data and it is confirmed that these road agencies have unsealed roads that are impacted by the same independent explanatory variables found in this study. The models cannot yet provide a basis for determining the road deterioration attributable to heavy vehicles for charging purposes because heavy vehicle road use is not a statistically significant variable in RD modelling. (Author/publisher)
Samenvatting