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GreenRoadsTM using a credit system to quantify the water quality during wet periods (Waters 2009). The degree of environmental sustainability. It includes New Zealand Otta seal provides a use for recycled five of the seven environmental sustainability impact motor oil and asphalt plant reject aggregate and, if factor areas. The 2009 operations program can eas- properly applied, has a service life of 2 to 3 years in ily be expanded to include pavement preservation New Zealand. and maintenance operations. To do so will entail addi- The combination of the maintenance culture shift, tional work to develop the comparative environ- the incentive/disincentive scheme that is part of the mental foot-printing data necessary to differentiate PSMC, and the national commitment to environmen- between the suite of pavement preservation and main- tal responsibility has led to a very robust pavement tenance treatments. Consequently, the spreadsheet- preservation and maintenance program that empha- based rating system could be leveraged into a very sizes preservation over repair (Waters 2004). Addi- powerful tool to enhance environmental sustainability tionally, the prescribed pavement design method is in North America. based on life-cycle cost analysis. This results in an effective standard where average annual daily traffic Case Study 8: New Zealand Transport Agency-- must exceed approximately 25,000 vehicles per day Sustainable Land Transport to meet a warrant for hot-mix asphalt or portland cement concrete pavement (TNZ 2005). Table 15 New Zealand has a record of aggressive pave- ment preservation and a maintenance program based lists the NZTA program details. on its performance-specified maintenance contract- As noted in the summary table, NZTA has the ing (PSMC) system (Manion and Tighe 2008). The most robust pavement preservation and maintenance nation's highway system typically consists of "a environmental sustainability program reviewed in this sprayed chip seal over unbound granular base and synthesis. Not only does it cover the full range of sub-base layers" (Pidwerbesky and Waters 1997). environmental sustainability impact factor areas cat- The New Zealand Transport Agency (NZTA) pro- egories, but it is coupled with a life-cycle cost-based vides for district-level pavement maintenance pavement design method and a performance-based planning in six of the seven environmental sustain- maintenance contracting system that create an un- ability factors. The program is outsourced and the bending predisposition to environmental sustainabil- PSMCs are controlled through a sophisticated set of ity in pavement maintenance. more than 200 key performance indicators (KPIs). Most KPIs are established using direct measure- Results from Case Studies ments of physical properties such as macrotexture and skid resistance. As a result of this feature, this Overall, the information gathered through the system is slightly different from traditional pavement three study instruments indicates that there are some management systems in North America. good environmental sustainability plans and proto- The change in pavement maintenance culture cols in place. Although most are focused on design has supported the development of green pavement and construction, in a majority of cases the principles maintenance technologies such as the Ultra-High on which they are based can directly be applied to Pressure Water Cutter that restores pavement macro- pavement preservation and maintenance programs. texture without consuming any virgin materials. The identified environmental sustainability impact Another innovation is a form of microsurfacing that factor areas are relevant to the current preservation is used in areas with low volumes of traffic, but with and maintenance practices and, although there were high shear stresses such as mountain curves on grades no case studies or tools found in the literature that where chip seals fail and hot mix is not justified. The cover all seven factors, they are mentioned at vary- treatment was deliberately designed to minimize the ing levels. In addition, many of the available tools total amount of virgin material consumed in its pro- are not necessarily specific to pavement infrastruc- duction (Pidwerbesky and Waters 1997). NZTA must ture. However, the frameworks and protocols serve maintain 40,000 km of gravel-surfaced roads. A as a foundation upon which they can be adapted to sustainable maintenance technique is the use of the pavements. New Zealand Otta seals (note these are different from Table 16 is a synopsis of the eight case studies those used in the United States) to improve air quality and how their programs cover the seven environ- during dry periods and reduce erosion and enhance mental sustainability impact factor areas categories. 20

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Table 15 NZTA sustainable land transport Sustainability Impact Factor Area Description/Relevance to Pavement Preservation and Maintenance Virgin Material Usage/Alternative Emphasis on limiting virgin material usage and alternative material Material Usage usage is stressed in the program No direct quantification of pavement treatments and associated material usage Program for Pavement In-Service Contracting structure creates a continuous monitoring of pavement Monitoring and Management condition Quantification is part and parcel of the contract monthly payment mechanism Noise Cites standards for measures for reducing pavement noise No direct quantification of pavement treatments and associated noise reduction Air Quality/Emissions Emphasis is on minimizing congestion in work zones and thus it reduces emissions Strict standards for air quality during all phases of pavement construction and maintenance No direct quantification of pavement treatments and associated air quality Water Quality Includes volume and area limits on soil disturbance to reduce sediment into streams and ensure proper storm water management Quantification of pavement treatments impact associated water quality via testing protocols Energy Usage Whole life approach to minimizing petroleum consumption No direct quantification of pavement treatments and associated energy usage reductions Other: Life-Cycle Cost Based Mandated design method is based on life-cycle cost calculations and Pavement Design AADT. Hot mix is only warranted for roads with AADT > 25,000. PCCP warrants are only for high-volume urban motorways Method inherently reduces the amount of energy and virgin material required for the national highway system AADT = average annual daily traffic; PCCP = portland cement concrete pavement. Table 16 Summary of case study agency sustainability programs Case Virgin Alternative Pavement In-Service Study Material Material Monitoring and Air Quality/ Water Energy Agency Usage Usage Management Noise Emissions Quality Usage ADOT NYSDOT ODOT WSDOT MTO NZTA PSCC Phila. Totals 7 7 5 4 7 6 5 21