A train carrying 40 passengers bound for Kiama clipped a stationary freight train as it passed, according to an Australian Transport Safety Bureau investigation.
The incident took place just after 6pm on July 21 last year in the southern Sydney suburb of Loftus.
A Pacific National freight train from Port Kembla had stopped at a signal when the southbound Kiama train passed.
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As it passed, the passenger train clipped an air filter hatch that was sticking out of the side of the freight train.
The impact smashed several windows and damaged doors on the Kiama-bound train, which was carrying as many as 40 passengers.
The driver of the passenger train heard the noise of the collision and stopped at Loftus.
However, the freight train driver didn't hear a thing and, unaware of the collision, proceeded towards Sydney.
The driver had to be directed to stop shortly afterwards.
The investigation found the train hit an open hatch on the side of the Pacific National freight train.
"The unsecured air filter hatch on [the freight train] probably opened after passing Loftus or was drawn outwards by the air pressure associated with the passing of [the passenger train] when it was struck," the investigation stated.
Fortunately no-one was injured in the incident.
To avoid a repeat of the incident Pacific National has undertaken an inspection of these hatches on all its trains to check the integrity of the locks and hinges.
During the inspections they also discovered a second hatch that could exceed the outline of the train if left open.
To deal with both hatches Pacific National created a design change that installed a secondary latch.
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