{'fraction_non_alphanumeric': 0.015215553677092139, 'fraction_numerical': 0.0008453085376162299, 'mean_word_length': 5.21259842519685, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Identification of High-Speed Rail Ballast Flight Risk Factors and Risk Mitigation Strategies

With the development of high speed rail (HSR) systems around the world during the past 50 years, one of the observed phenomena that occur at the train-track interface is the “ballast flight”, a phenomenon where ballast particles become airborne during the passage of a train. This phenomenon occurs when a combination of both mechanical and aerodynamic forces generated mostly by the passage of the train cause a ballast particle to overcome gravity. Factors affecting ballast flight include aerodynamic conditions, track response, ground effects and atmospheric conditions. Damages to the railhead, train body, and adjacent structures as well as injuries to maintenance staff have been reported in the literature to result in a major maintenance cost and safety concern for HSR systems with ballasted track. Previous studies have used laboratory wind tunnel tests and large-scale field tests to verify the various causes and mechanisms of ballast flight, and theoretical models have been developed to simulate the phenomena. However, there are only few existing practical risk models formulated according to certain field and/or analytical occurrences and used to assess the risk of ballast flight under different HSR operating conditions. For example the French National Railways (SNCF) and the Spanish Railway Administration (ADIF) have developed models to assess the flying ballast. A comprehensive literature review is needed to identify all the risk factors relevant to potential HSR operational conditions in the U.S. This would enable the development of a risk model to assess the ballast flight risk. The purpose of this article is to present the planned framework by the University of Illinois at Urbana-Champaign to perform a full evaluation of risk factors that may contribute to ballast flight in the United States where HSR is now emerging. This findings will likely to provide a basic strategic development plan for ballast flight risk for HSR operations in the United States. The scope of the work will include an identification of operating and infrastructure conditions that may lead to ballast flight, a development of risk assessments and methodologies for HSR planners and operators in North America, thus allowing the development of safe HSR systems.