Insulating joints at crossings and junctions can suffer electrical failure due to metal shavings and other conductive contaminants that accumulate in the insulator gaps. Increasing joint distance from the diamond frog junction can reduce build-up of grease and other debris, but creates dead zones in which train cars and locomotives cannot be detected using traditional track circuits. Tie-mounted PD loops can be used to detect trains in these dead sections, but are highly vulnerable to damage and failure. The paper describes the design, testing, and implementation of a radar-based train detection system at a BNSF full flange bearing diamond frog junction with dead sections greater than 30 feet (FRA requirement is 35 feet or shortest wheel base of a locomotive, which is 30 feet at BNSF). Detection performance was evaluated at a test site over a five-month period, and contrasted with that of a surface-mounted presence detection loop system. Revenue service implementation at future sites includes vitally circuiting redundant radar sensors to provide equivalent protection for these dead sections.
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