Management of unpaved roads : developing a strategy and refining models

Abstract

The Western Cape has a large network of 25 300 km of unpaved roads. The unpaved road network is managed within the framework of the Unpaved Road Maintenance System with the assistance of five District Municipalities. The Road Network Management Branch is under continuous pressure to provide and maintain a safe and economic road network with limited funds. The Branch’s objective for the unpaved road network is to maintain and build high performance and cost effective gravel roads that will last longer, provide a good average riding quality and a safe riding surface. Only a fraction of the gravel loss per annum has been replaced during the last decade, resulting in the average gravel thickness decreasing from 75 mm in 1990 to 23 mm in 2009 and remaining at that thickness since then. Consequently, there has been a significant increase in very poor roads. The poor state of the unpaved network makes it is imperative that the Branch use its available funding in the most effective and efficient manner through application of the best processes and technology. The objective of the paper is to present the approach taken by the Branch to develop and implement a turnaround strategy that includes the refinement of HDM-4 prediction models. The paper covers an introduction to the problem, describes the Unpaved Road Maintenance System, the strategy and plan, which includes the level of service and treatment activities for planned maintenance, the demand-supply model for determining the required supply of gravel and the number of regravel teams for a target average thickness of gravel on the network. The development of the strategy and plan enables the connection of tactical planning and operational maintenance activities with the strategic objectives and encourages discussion on cost, performance and risk to spur on improvements that should lead to better network performance. The revival and redevelopment of management information systems with improved modules and a new Risk Register module providing planning and operational support, and new functionality in the Materials Information Management System is described. Improving techniques and technologies through blading optimisation, crushing of material, rolling after blading, tyre dragging and blading maintenance strategy development is also covered. The calibration and adjustment of the HDM-4 performance models to incorporate the quality of construction, specific blading methods as well as other treatments is ongoing. The optimum maintenance strategy on a road could consist of different treatments during the maintenance life-cycle and that different strategies are required depending on materials, climate, topography (horizontal and vertical alignment) and traffic. In conclusion, the significance of this work lies in the development of a strategy that enables the connection of tactical planning and operational maintenance activities on the unpaved road network with the strategic objectives and encourages discussion on cost, performance and risk, while spurring on improvements that lead to more effective management, better network performance and outcomes for the community.