Greenroads ( www.greenroads.us ) is a performance metric for sustainable practices associated with the design and construction of roads. It assigns points for approved sustainable choices/practices and can be used to assess roadway project sustainability measures based on total points. Such a metric can (1) provide a quantitative means of sustainability assessment, (2) allow informed sustainability decisions, (3) provide baseline sustainability standards, and (4) stimulate improvement and innovation in integrated roadway sustainability. This paper describes Greenroads version 1.0, which consists of 11 requirements and 37 voluntary practices that can be used as a project-level sustainability performance metric. Development efforts and a Washington State Department of Transportation (WSDOT) case study suggest (1) existing project data can serve as the data source for performance assessment, (2) some requirements and voluntary actions need refinement, (3) projects need to treat sustainability in a holistic manner to meet a reasonable sustainability performance standard, (4), the financial impact of Greenroads use must be studied, and (5) several pilot projects are needed. The Greenroads sustainability performance metric can be a viable means of project-level sustainability performance assessment and decision support.

Greenroads, a system used to rate the sustainability of roadway projects, was used to evaluate 105 roadway and bridge projects in the United States for sustainable design and construction practices at various life cycle stages. A sustainability rating system can be a practical tool to help quantify and measure sustainability for a roadway project. The purpose of the investigation was to determine the state of the practice in sustainable roadway design and construction by application of Greenroads to a variety of actual projects. Forty projects identified as sustainable were compared with 65 typical projects representing conventional practice. The objectives of this study were to (a) identify trends in Greenroads project ratings, (b) benchmark the current state of the practice and identify potential areas for improved sustainability performance, (c) determine whether Greenroads can differentiate among projects on the basis of their sustainability efforts, and (d) identify the implications of these findings to practice. The results show that (a) some credits and categories are easily achieved, although achievement of others is more challenging and offers opportunities for improved environmental performance; (b) typical roadway projects tend to meet environmental regulatory standards but rarely do much more even when possible; therefore, they score fewer points for credits that focus on environmental benefits beyond the regulatory minimum; (c) contractors and materials suppliers appear to have unrealized opportunities to contribute; and (d) an early emphasis on the environment during project development appears to differentiate between typical and sustainable projects and manifest as higher Greenroads scores.

The rapid growth in popularity of sustainable roadway certification systems suggests that a holistic evaluation of rating systems and a retrospective examination of sustainable roadway practices are warranted. Regardless of underlying sustainability definitions guiding any transportation project rating system, literature reveals that there is little consensus on how rating systems should ultimately weigh human, environmental, and economic needs relative to each other. This research is the first effort to use documented project certification data, a unique data set consisting of 28 Greenroads certified projects, to investigate the state of practice of sustainability rating systems and sustainable construction practices. By using quantitative and qualitative analyses, this study identifies and explores common strategies used by project teams to achieve sustainability under the Greenroads rating system. This study argues that sustainable projects make a quantifiable difference in performance compared with typical projects. However, projects that pursue independent third-party sustainability certification should strategize their expectations and manage performance expectations accordingly because this research shows that self-evaluations overestimate final scores by an average of 15%. Although the Greenroads framework allows for many combinations of scores, certified projects exhibit score breakdowns similar to both the rating system and other certified projects. Because the majority of points awarded by Greenroads is limited to a subset of core credits, this study proposes that sustainable practices revolve around current standards of practice, perceived practicality, or economic benefits. Future research should focus on identifying similar patterns in other roadway sustainability rating systems to explore the gap between sustainable knowledge and practice.

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