All maintenance and construction projects on New Zealand public roads are contracted out. In combination with constrained budgets limiting resurfacing treatment lengths, contracting out has encouraged substantial investment by industry in new developments and innovation to extend the road maintenance budget. A number of cost-effective, innovative surfacing treatments have been developed in New Zealand for low-volume roads. A sample of these innovative surfacing treatments is presented. Ultra-high-pressure watercutting is being used to improve both macro-texture and microtexture of surfacings on low-volume roads, thereby extending the life of those surfacings. Modern computer-controlled sprayers have been developed to apply bitumen at rates that vary transversely across the lane width. These sprayers are also used when chip seal surfaces have insufficient macrotexture in the wheel tracks, as well as a preventive measure for binder rise in the future. Ultrathin textured gap-graded hot mixes are being used in high-stress, high-trafficked areas. The monitoring of the treatments includes skid resistance, texture depth, performance, and safety (numbers of accidents) for 6 years or more. The performance to date of these treatments and strategies is discussed. In addition, a research project under way is aimed at developing more robust guidelines for selecting binder grade on the basis of climatic conditions to improve the performance of surfacings. Interim results of this project are discussed. Combining the wide range of state-of-the-art surfacing treatments with best practice in asset management in a cost-effective sealing and maintenance program has resulted in significant improvements in road safety, reduced accident costs, and improved performance and substantially reduces the potential for accidents.

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Low-volume roads require cost-effective maintenance methods to minimize the amount of money spent on them while maximizing the engineering properties required to furnish the required levels of service. Skid resistance is an engineering property that is important for any road. Because chip sealing is a tried-and-true pavement preservation method, it often is used as the primary maintenance treatment of these roads. Unfortunately, chip seals are prone to flushing in the wheelpaths, which creates a loss of skid resistance. The economics of replacing strip sealing using conventional chip seal in the wheelpaths with the ultra-high-pressure watercutter used in New Zealand are explored. An economic analysis of typical low-volume roads on the basis of case studies found in Texas is conducted to determine the life-cycle costs of using both options on each case study project. The study applies the FHWA pavement life-cycle cost methodology, and the results are reported on a net-present-value basis to permit assessment of both methodologies. The analysis is conducted on two levels. First, a traditional deterministic life-cycle cost analysis is performed, and that is followed by a stochastic analysis of life-cycle cost using a Monte Carlo simulation. It is concluded that the watercutter is an economically viable alternative to strip sealing with the benefit of restoring the macrotexture without exacerbating the condition that caused the loss of skid resistance in the first place. It also allows the desired engineering objective to be achieved without additional consumption of asphalt binder or aggregate, thus making an environmentally sustainable alternative as well.

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