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Sustainability Impact Factor Areas make good use of available materials. The primary focus of this area is to consider the Measuring environmental sustainability is an reduced need for virgin material usage and emerging field in the transportation industry, and demand of virgin materials for treatments. even more so with respect to the pavement mainte- Many maintenance treatments involve in-place nance treatment selection process. The literature is recycling, which enables re-use of the materi- rife with newly coined terms to describe a given als already committed to roadways. Prolonging treatment's impact on the environment (Takamura the time between major rehabilitation and et al. 2001; James 2006; Ball et al. 2008; Chaignon reconstruction through proper pavement treat- and Mueller 2009; Lane 2010; Muench 2010). "The ment selection is an effective way to reduce vir- terms `Green,' `Sustainable Development,' `Environ- gin material usage. mental Impact,' `Energy Efficiency,' `Global Warm- 2. Alternative material usage examines the oppor- ing,' `Greenhouse Gases,' and `Eco-efficiency,' are tunity to recycle materials and to use other becoming more widely recognized . . . " (Chehovitz materials in the pavement structure during and Galehouse 2010). preservation and maintenance. This could Unfortunately, each article or manual focuses its mean incorporating reclaimed asphalt pave- evaluation of environmental impact on a different ment, recycled concrete aggregate, recycled set of impacts. For example, Takamura et al. (2001) asphalt shingles, recycled rubber tire, glass, or coined the term "eco-efficiency" to describe the com- any other materials that might be appropriate. parative analysis of six parameters: virgin material Proper processing of these materials can result consumption, energy consumption, land use, emis- in equivalent performance to virgin aggregate sions, toxicity, and risk potential. Pittenger's research (Infraguide 2005). Careful blending and (2010) included virgin material consumption, life- crushing of recycled materials is required to cycle cost, and a factor from the Greenroads certifi- achieve consistent gradation and performance cation program (Muench 2010); whereas Chehovitz of the material (Infraguide 2005). and Galehouse (2010) confined their analysis to 3. Programs for Pavement In-Service Monitoring greenhouse gas emissions and energy consumption. and Management assists agencies in finding the Thus, it is difficult to adopt a single, universally rec- right treatment for the right pavement at the ognized term to identify the process of evaluating right time. Robust information systems help competing pavement preservation and maintenance determine existing and forecasted pavement treatment options on the basis of relative environ- conditions so that decisions can be accurately mental sustainability. made and funds programmed for network The AASHTO Center for Environmental Excel- improvements. Pavement in-service monitor- lence (CEE) provides a basis for identifying and pro- ing and management would consider the life- moting environmental excellence in the efficient cycle and associated serviceability of the delivery of transportation services (Kober 2009). The treatment. CEE evaluates sustainability parameters by identify- 4. Noise is defined as the unwanted or excessive ing focus areas. Consequently, seven sustainability sound associated with pavement construction impact factor areas identified by the CEE will be con- and improvements. Studies show that the most sidered in this synthesis. Each one of the areas and pervasive sources of noise in the environment how they relate to pavement preservation and main- relate to transportation. Therefore, noise is tenance treatments is described herein. It should be examined as an environmental sustainability noted that other life-cycle assessment tools such as factor area whereby pavement preservation and the ISO 14040 Standard are available and many of maintenance treatments are evaluated on their these do cite other environmental sustainability noise impacts (CEE 2010a). impact factors (ISO 2006). However, for the purpose 5. Air quality/emissions examines six principal of this synthesis, the seven aforementioned factors air pollutants, namely carbon monoxide, lead, have been examined and are described here. nitrogen dioxide, ozone, particulate matter, and 1. Virgin material usage examines reducing the sulfur dioxide (CEE 2010b). The intent is to need to use nonrenewable resources. Pavement assess each pavement preservation and main- materials can be expensive and some resources tenance treatment in terms of these pollutants. may be limited; therefore, it is important to This would involve both calculations for the 5