Guidelines on developing performance metrics for evaluating transportation sustainability

Transportation systems have a significant impact on environmental, social, and economic sustainability. Traditional transportation performance metrics, which tend to focus on vehicle mobility and congestion, fail to assess the degree to which transportation planning leads to sustainable outcomes. Lacking appropriate metrics, transportation managers and policy- makers often do not have sufficient information to make decisions that consider sustainability as an outcome. Accordingly, this paper focuses on the process for developing such metrics in the form of a composite index. The intent of this paper is not to provide a singular, definitive index; rather, the goal is to provide guidance into the issues of selecting an appropriate index or developing their own. We begin by reviewing the existing literature on indicator selection criteria, examining the construction of composite indices, and exploring existing rating systems. Building on this knowledge, wedescribe the process for creating a systematic tool for assessing sustainable transportation called the Transportation Index for Sustainable Places (TISP). We also provide an example of one element of the TISP to illustrate the necessary steps involved in the ranking process.