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78 Shared Use of Railroad Infrastructure with Noncompliant Public Transit Rail Vehicles: A Practitioner's Guide Collision Safety of the Demonstration Project Project sponsors will have the burden of proof to satisfy the FRA that equivalent safety would be achieved by the chosen technology and operating methods. The project team has identified three key issues related to federal regulatory acceptance for a concurrent shared-track demon- stration project. 1. Understanding the severity of consequences of collisions between a light passenger rail car and conventional freight equipment through structural analysis. The result of collision may not be catastrophic. 2. Understanding differences in the rail-highway grade crossing risks posed by comparatively lighter rail vehicles. The grade crossing collision risks should be appropriately managed with due consideration to the speed of light rail cars, braking capabilities, and the type of traffic crossing over the railroad. 3. Demonstrating a consolidated equivalent level of safety in all aspects of the proposed opera- tions. A risk analysis (safety case) specific to the line, demonstrating that the combination of train control system and other mitigation measures makes the system at least as safe as a stand alone light rail line or a conventional commuter rail line. These issues are valid concerns to be addressed in a waiver petition for demonstration or pilot operation of concurrent shared-track. However, the transit system should not be held to a higher standard than other modes, and the null alternative--risks if nothing is done--needs to be considered. Collisions Between Light Passenger Rail Cars and Conventional Equipment The severity of collisions is the leading safety concern with concurrent shared-track opera- tions. Many options are available to reduce the frequency of train-train and intrusion collisions, but the risk cannot be entirely eliminated. Much less information about the severity of conse- quences is available. Because the practice is relatively new and because measures to reduce the likelihood of collisions have been very effective, no meaningful historical accident information exists. If current and planned preventive measures are successful it will remain that way. Only very simple analyses of hypothetical collisions have been performed. For the limited concurrent shared-track operations, such as the River LINE and San Diego Trolley, the FRA was provided with a qualitative risk assessment (performed by the transit agency) to provide safety assurance and took no exception to proposed train control systems and operating procedures for ensuring a fail-safe train separation. For more extensive concurrent operations, a more detailed analysis may be required. This analysis might include: Formal three-dimensional structural crush and collision dynamics analyses of representative collision scenarios; and A quantitative risk analysis that takes into account the results of the collision analysis and the expected performance of proposed train control systems. Application of Risk Analyses Methodology to the Demonstration Project The deficiencies of risk analyses are particularly apparent for concurrent shared-track proj- ects. There is little actual accident or incident data. All operations to date entail some form of temporal separation, and are not truly concurrent. Ironically, due to the excellent safety record of many rail transit systems, there is a dearth of transferable data for risk modeling purposes. An example of this lack of information can be seen in Europe where tram trains and other forms of commingled shared-track arrangements are more prevalent; accident experience with these types of operation are very meager. The risk model should reflect parameters considered appropriate to the shared-track envi- ronment. The analyses also should incorporate the impacts of actions that the prospective oper-