Outdated circuit wiring diagram leads to signalling irregularity

Train DP41 at the platform with signal EJ45 and the 705 points incorrectly set

A newly-replaced points machine at Brisbane’s Eagle Junction station resulted in a signal displaying an incorrect authority to proceed to a suburban passenger train as it had been pre-wired in accordance with an outdated master circuit diagram.

The incident occurred on 23 September 2018 when signal EJ45 displayed an invalid authority for the positioning of the points ahead for passenger train DP41, which was about to depart the station. Both the driver and a signal electrician noticed the irregularity and reported it to the network control officer, who directed the driver to remain at the platform. A short time later, another train approached and crossed over the conflicting route.

“The actions of the driver, the network control officer and the signal electrician in identifying the irregularity and stopping the train departing Eagle Junction mitigated the potential for a collision,” noted ATSB Director Transport Safety, Dr Stuart Godley.

An ATSB investigation found that the new points machine was pre-wired in accordance with the master circuit diagram. However, it was likely that the master circuit diagram was not updated to reflect modifications made to the old points machine to accommodate the Airport Line (which opened in 2001 and branches off the Queensland Rail City network at Eagle Junction).

Accurate and up-to-date engineering documents correlating with in‑field equipment are fundamental to the effectiveness of an engineered interlocked signalling system to maintain train separation.

“This introduced an inadvertent wiring error, resulting in the signal interlocking systems indicating the points were set in the normal position, whether they were or not,” Dr Godley said.

“Accurate and up-to-date engineering documents correlating with in‑field equipment are fundamental to the effectiveness of an engineered interlocked signalling system to maintain train separation.”

Queensland Rail have since introduced a procedure requiring correlation between the in-field signalling equipment and the master circuit diagrams before safety critical work is undertaken, Dr Godley noted.

Read the investigation report RO-2018-020: Signalling irregularity at Eagle Junction, Queensland, on 23 September 2018

Last update 05 June 2020

Final report

RO-2018-020: Signalling irregularity at Eagle Junction, Queensland, on 23 September 2018