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that although environmental sustainability is not A New Zealand study confirmed this assertion when explicitly mentioned in the mission and vision it found: "Current indications are that chip sealing statements of most agencies, many do include the emulsions typically would be classified as safe . . . " three elements (Amekudzi and Jean 2007; Ramani (Ball et al. 2008). Thus, adding an environmental et al. 2009). sustainability factor to the pavement preservation The concept of environmental sustainability and and maintenance decision-making process is both how it can be employed in various practice areas is timely and appropriate. gaining wide support from the general public, gov- ernments, and professionals (Chan and Tighe 2010; Key Definitions Muench 2010). The need of quantifying sustainable practices is also challenging and requires a holistic The synthesis will use a number of definitions. It approach. The initiatives by LEEDTM (USGBC 2010), is important for the reader to understand the specific Greenroads (Muench 2010), GreenLITES (NYSDOT definition of each of the terms to gain a full under- 2009), and GreenPave (MTO 2010) certification pro- standing of the meaning of this study. The most grams are leading examples of programs that pro- notable key definitions for this work include pave- mote and quantify sustainable practices (Chan and ment maintenance versus pavement preservation. For Tighe 2010). In addition, there are several other ini- this study, the current FHWA definitions for pave- tiatives such as PaLATE (Horvath 2009), EIO-LCA ment preservation and maintenance terminology have (EIOLCA 2010), and some industry initiatives been used. These definitions provide the basis of that will be described later in the report. However, assessment for this synthesis. although it is notable that many of the environmen- Pavement preservation is "a program employing tal sustainability initiatives consider preservation a network level, long-term strategy that enhances and maintenance treatments and their contributions pavement performance by using an integrated, cost- to long life pavements, there is limited explicit effective set of practices that extend pavement life, assessment of those treatments in terms of environ- improve safety, and meet motorist expectations" mental performance. (FHWA 2005). Pavement preservation is comprised As noted in FHWA's newsletter, Strategic, Safe of the following activities: and Sustainable: Today's Vision for Pavements, Preventive maintenance is "a planned strat- environmental sustainability is of critical importance egy of cost-effective treatments to an existing (Stephanos 2009). It was noted in that article, in the roadway system and its appurtenances that new decade of environmental awareness, that max- preserves the system, retards future deteriora- imizing recycled materials in pavement construction tion, and maintains or improves the functional and rehabilitation is a priority and this is further condition of the system (without significantly advanced through the FHWA participation in Green increasing the structural capacity)" (FHWA Highways Partnership, which is an attempt to align 2005). various state specifications for using recycled ma- Routine maintenance "consists of work that terials. Other initiatives include using warm mix that is planned and performed on a routine basis generates fewer emissions and conducting research to maintain and preserve the condition of the on expanding the types and amount of fly ash that highway system or to respond to specific can be used in concrete paving. Although these ini- conditions and events that restore the high- tiatives tend to focus primarily on usage in pavement way system to an adequate level of service" construction and rehabilitation treatments, they are (FHWA 2005). also an important part of pavement preservation and Minor pavement rehabilitation consists of maintenance treatments. "structural enhancements made to the existing Additionally, recent research in France and New sections to eliminate age-related, top-down sur- Zealand (Ball et al. 2008) mirrors a U.S. movement face cracking that develops in flexible pave- from solvent-based binders toward water-based emul- ments due to environmental exposure. Because sion binders for use in pavement preservation and of the non-structural nature of minor rehabil- maintenance treatments as a result of concern for the itation techniques, these types of rehabilita- environment. Emulsions are "more . . . environmen- tion techniques are placed in the category of tally friendly that . . . cut back asphalts" (James 2006). pavement preservation" (FHWA 2005). 4