Prior to this derailment, neither training nor procedures mandated the guard to exercise control over the speed of the train by using the emergency brake pipe cock ("the tail"). Apart from the driver being considered to be the sole operator of the train, the emergency brake pipe cock does not provide the same degree of control over the automatic brake as a proper brake valve. The consensus among train crews was that a sudden emergency application from the rear could cause a breakaway (which is in fact not possible, as the cock does not apply the brakes solely to the rear car but rather uniformly along the full length of the train), and there was some evidence from previous accidents to validate such an opinion, however these were not involving the modern multiple-unit train design of which the Tangara is an example.