Wednesday, August 2, 2017

Understanding Uncertainty in Forecasting and Decision Making

Map of the proposed Purple Line in Maryland. Image Credit:
According to an article from, well-intentioned legislation may provide loopholes that hinder the forward progress of transportation projects. For example, though the National Environmental Protection Act (NEPA) strives to support “an enjoyable harmony between man and his environment,” the law has been used as a tool to slow down or halt transportation projects, even if the projects do not pose a threat to the surrounding environment. In 2014, the FTA approved funding for a 16-mile light rail with 21 stations that would connect communities across two large suburban counties in Washington, D.C. In summer 2016 a NEPA lawsuit put the project on hold while the court required the FTA to provide more detailed ridership projections to the year 2040. The author posits that given the uncertainties of technological advancement, it is difficult to predict future transportation trends with perfect accuracy. Modeling and forecasting remain important tools for planners and decision-makers, however it is important to understand that without a crystal ball, decisions must be made in the context of some uncertainty. For more on this topic, look for Alan Ehrenhalt's article at

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