Pavement Life Cycle Assessment Workshop: Discussion Summary and Guidelines

Operation of the state and national pavement network, which includes both its construction and maintenance, incurs the use of large amounts of energy and natural resources, and results in the emission of significant quantities of greenhouse gases (GHGs), criteria air pollutants, and water pollutants. As recognition of the harm caused by these substances and the costs of resources has increased, significant efforts are now underway to mitigate them and their environmental impacts. However, as is the case whenever a systemic process is changed to reduce its environmental impact, the possibility exists that policy changes can have unintended negative consequences that can actually cause greater environmental harm. The risk of unintended negative consequences is greatest when changes are made that affect one part of a system or life-cycle phase, but the effects of the changes on the rest of the system and the other life-cycle phases are not evaluated. Life cycle assessment (LCA) is an approach for investigating the consequences of changes that when properly applied considers both systems analysis and the entire life cycle. Although there have been several LCA studies on the subject of pavement, nearly all of them have focused on pavement type selection (asphalt or concrete) for new pavements for a narrow range of conditions, and the results have offered conflicting answers to questions about the resulting environmental impacts. This inconsistency is due to the lack of consistent LCA practice and to use of different data sources. Among the specific recurring problems found in LCA are unrepresentative functional units and analysis periods, a lack of transparency in impact allocation of the bitumen-refining process, and incomplete consideration of the full life cycle. Until these issues are resolved, they will continue to make it difficult to use LCA for pavement-related decision making. To address these issues for Caltrans and interested collaborators, the University of California Pavement Research Center (UCPRC, Davis and Berkeley) and the University of California Institute of Transportation Studies (Berkeley and Davis) have undertaken work together on recommending common practices for conducting LCA for pavements. The first-stage research product arising from this work intended for pavement LCA practitioners is the UCPRC Pavement LCA Guideline, which includes a highlevel LCA framework for pavements, as well as some recommended data and models that have been used in California and elsewhere in the U.S. In May 2010, a workshop was held in Davis, California, to discuss the first draft of this guideline, and to answer some key questions regarding LCA practice and the application of the results. This technical memorandum contains a summary of the workshop discussions and the final draft Guideline based on the discussions.