; (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); and (5) research to understand new or developing technologies. (c) Plan elements (1) Risk-based Each defect detection system plan required under the final rule issued pursuant to subsection (d) shall be risk-based. (2) Contents Each plan referred to in paragraph (1) shall include— (A) a summary of the railroad’s proposed defect detector network, including— (i) how the network will reduce the risk of incidents near population centers and on high-hazard train routes; and (ii) a description of how the network will be implemented by the deadline set forth in subsection (d)(1)(B); and (B) a description of how the railroad's defect detection system meets or exceeds the defect detection performance standards described in subsection (d)(1)(D); (C) except as provided in paragraph (3), a risk-based approach for identifying overheated wheel bearings that require the placement of the types and spacing of defect detectors— (i) for main lines traveling within an urbanized area with a population of at least 75,000, at a distance that provides for any train operating along the railroad’s route to undergo detection not less than 10 miles before entering such an area; (ii) for main lines not equipped with acoustic bearing detectors or other similar technology, at a distance averaging 15 route miles to the extent possible based on the physical characteristics of the route; and (iii) for main lines equipped with acoustic bearing detectors or other similar technology, at a distance averaging 20 route miles to the extent possible based on the physical characteristics of the route along which such detectors are being installed; (D) the types and spacing of other wayside defect detectors required to be placed, to the extent such detectors are utilized