Assessing the Effectiveness of Impact-Mitigating Countermeasures at Reducing Fatality Risk in the NYC Subway

The New York City subway system is the preferred mode of transportation for millions of commuters daily and is an affordable alternative to other transportation options. Despite this utility, the subway has had a public safety problem going back decades. In NYC alone, over 50 deaths and dozens of debilitating injuries are caused by train-pedestrian collisions on a yearly basis. Many conventional solutions, such as platform doors, are not possible due to the subway’s aging infrastructure, excessive installation costs, and accessibility issues. To address the safety concerns within NYC subway, the Federal Transit Administration funded a project specifically aimed at developing and evaluating train-mounted impact-mitigating countermeasures. The goal of this thesis was to evaluate the effectiveness of a potential countermeasure and assess its benefit to public safety. The first step was to understand the distribution of impact conditions seen in the subway by studying incident reports. These statistics helped establish performance targets for the countermeasure and recognize design challenges related to train and station geometry. It was essential for the countermeasure to reduce impact severity and rebound. For this purpose, energy absorbing materials that exhibited the desired physical properties were identified and characterized through compression testing. The effectiveness of these materials was assessed through a combination of finite element simulations and sled tests. It was estimated that a countermeasure attached to the train front could reduce fatalities in the New York City subway by more than 80%, bringing the annual fatality count to under ten per year. A benefit-cost analysis was conducted using the predicted countermeasure effectiveness and rough cost estimates. Given the most conservative estimation for installation and maintenance cost, the net value of the project was evaluated to be one billion US Dollars over a 50-year period. This analysis indicates that a countermeasure could drastically improve public safety in the subway.