“…Consequently, most degraded crossings are reactively replaced when they reach severe degradation. The limitations of manual inspection motivate the development of on-board monitoring technologies, such as ultrasonic measurement [ 4 , 5 ], eddy current testing [ 6 , 7 ], magnetic induction [ 8 ], image recognition [ 9 , 10 , 11 ], vibration-based inspection [ 12 , 13 ], guided-wave inspection [ 14 ], radio detection and ranging sensors [ 15 , 16 ], thermography [ 17 , 18 ], acoustic emission systems [ 19 , 20 ] and ground-penetrating radar [ 21 , 22 ].…”