138 protocols for actual construction projects hinders the ability to quantify tangible environmental and economic benefits that can be achieved through reuse and recycling in pavement design and construction. Carpenter et al. (4) illustrate how a life-cycle assessment (LCA) approach can be used to quantify the environmental impacts of using recycled materials in lieu of conventional construction materials and remark on the economic benefit that can be accrued using recycled materials in roadway construction. However, their analysis does not include rehabilitation activities, which are some of the most energy- intensive phases in the roadway life cycle. They also do not quantify the economic benefits from using recycled materials. In the context of sustainability, direct comparisons of the life-cycle cost using recycled materials instead of conventional materials are important. In this study, comparative environmental and economic life-cycle analyses were conducted to quantify the environmental and economic benefits that could be accrued by using recycled materials when constructing a 4.7-km-long section of the Burlington Bypass in southeastern Wisconsin. Rehabilitation activities were explicitly included in the life-cycle analysis using the international roughness index (IRI) as a metric to define when rehabilitation would be required, as suggested by FHWA (5). The benefits illustrated in this quantita- tive analysis are expected to encourage wider adoption of recycled materials in roadway construction and rehabilitation. EVALUATION OF THE BURLINGTON BYPASS A comparative life-cycle analysis was conducted for construction of a section of Wisconsin State Highway 36/83 near Burlington, Wisconsin (the Burlington Bypass), assuming that the pavement would be constructed with conventional or recycled materials. The Burlington Bypass consists of 17.7 km of highway that routes traffic on WIS-11 and WIS-36/83 around the City of Burlington, Wisconsin. The bypass is intended to improve safety, reduce delays, and to provide an efficient travel pattern that reduces truck traffic in the downtown area of the city of Burlington (6). The western portion of the bypass is being constructed between spring 2008 and fall 2010. A 4.7-km-long section of the western portion of the bypass was analyzed in this study. A flowchart for the evaluation procedure is shown in Figure 1. The steps include creating pavement designs using conventional and recycled materials, predicting the service life of each design, iden- tifying rehabilitation strategies, and conducting LCA and life-cycle cost analysis (LCCA). LCCA is a financial-based decision-making Quantitative Assessment of Environmental and Economic Benefits of Recycled Materials in Highway Construction Jin Cheol Lee, Tuncer B. Edil, James M. Tinjum, and Craig H. Benson The benefits of using recycled materials in highway pavements was assessed quantitatively by conducting life-cycle analysis and life-cycle cost analysis on pavements consisting of conventional and recycled materials for a highway construction project in Wisconsin. Results of the analysis indicate that using recycled materials in the base and subbase layers of a pavement can result in reductions in global warming potential (20%), energy consumption (16%), water consumption (11%), and hazardous waste generation (11%) while also extending the service life of the pavement. In addition, using recycled materials in the base and subbase layers can result in a life-cycle cost savings of 21%. The savings are even greater if landfill avoidance costs are considered for the recycled materials incorporated in the pavement. Extrapolation of the benefits to conditions nationwide indicates that modest changes in pavement design to incorporate recycled materials can contribute substantially to the emission reductions required to stabilize greenhouse gas emissions at current levels. New construction and rehabilitation of the roadway system in the United States occurs continuously to meet the nation’s transportation needs. These activities consume large amounts of natural materials and energy, produce wastes, and generate greenhouse gas emissions (1, 2). Thus any regional or national sustainability plan in the United States must account for roadway construction and rehabilitation. A sustainable approach to material consumption begins with design and planning that reuses and incorporates suitable by-products that would otherwise be disposed. Ideally, products can be designed so that recycling and reuse occur at all stages of the life-cycle, resulting in limited waste generation. For road construction, Gambatese and Rajendran (1) and Kibert (3) show that reuse and recycling can sig- nificantly contribute to more sustainable road construction practices. However, lack of comparative analysis methods, examples, and J. C. Lee, Recycled Materials Resource Center and Department of Civil and Environ- mental Engineering, 2231 Engineering Hall; T. B. Edil, Recycled Materials Resource Center and Department of Civil and Environmental Engineering, 2226 Engineering Hall; J. M. Tinjum, Engineering Professional Development and Department of Civil and Environmental Engineering, 2214 Engineering Hall; and C. H. Benson, Recycled Materials Resource Center, Geological Engineering, 2218 Engineering Hall, Univer- sity of Wisconsin–Madison, 1415 Engineering Drive, Madison, WI 53706-1691. Corresponding author: T. B. Edil, edil@engr.wisc.edu. Transportation Research Record: Journal of the Transportation Research Board, No. 2158, Transportation Research Board of the National Academies, Washington, D.C., 2010, pp. 138–142. DOI: 10.3141/2158-17