4. Indicators relating to precursors of accidents U.K.
Total and relative (to train-kilometres) number of precursors to accidents and a break down on the following types of precursor:
broken rail,
track buckle and other track misalignment,
wrong-side signalling failure,
signal passed at danger when passing a danger point,
signal passed at danger without passing a danger point,
broken wheel on rolling stock in service,
broken axle on rolling stock in service.
All precursors are to be reported, both those resulting and those not resulting in accidents. (A precursor resulting in a significant accident shall also be reported under indicators relating to precursors; a precursor not resulting in a significant accident shall only be reported under indicators relating to precursors).