Informing Roadway Sustainability Practices by Using Greenroads Certified Project Data

Abstract

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.