; and (ii) that has a maximum authorized speed for freight trains in excess of 25 miles per hour; and (B) intercity rail passenger transportation or commuter rail passenger transportation routes or segments over which high-hazard trains operate. (6) Physical characteristics The term physical characteristics means the physical terrain and operating considerations related to the physical terrain for the relevant main line. (b) Defect Detector Analysis Program The Secretary shall develop a program for the research, development, testing, and evaluation of defect detector systems to inform and support the rulemaking required under subsection (d) and the evaluation of plans under subsection (c), which shall include— (1) an evaluation of existing manufacturer recommended practices, industry-developed voluntary consensus technical standards, and railroad safety data to inform appropriate standards for commercially available defect detector systems and ensure the integrity and reliability of their use on the general railroad system, including standards relating to— (A) maintenance; (B) testing; (C) inspection; and (D) installation; (2) an assessment of existing alert thresholds and trending algorithms to determine appropriate metrics and levels to ensure that defect detector systems identify unsafe equipment or operations in time to take appropriate safety actions; (3) an evaluation of existing processes and procedures for decision making and communication of appropriate safety actions necessary to address unsafe equipment or operations, including— (A) stoppage of rail equipment; (B) setting out rail equipment; (C) train speed reduction; (D) diverting a train; and (E) inspection requirements; (4) research to understand the capabilities and limitations of existing technologies in use or developed to better assess the plans required under the final rule issued pursuant to subsection (c)