A faulty signal lantern could have been a factor in a crash between two trams that injured six people and disrupted traffic for hours.
The trams crashed at the intersection of Victoria Parade and Nicholson Street in Melbourne on September 20, sparking an investigation led by the Office of the Chief Investigator for Transport Safety.
Its preliminary report, released on Friday, reveals a set of points along the Nicholson Street tracks turned the north-bound tram off its intended course and into the path of the south-bound tram.
"The driver of (the north-bound) tram 6058 had expected to travel straight across the intersection," the report reads.
"Tram 6058 had travelled through two sets of points.
"The first set of points were set for the straight, and the second set of points were set for the right turn."
The trams were travelling about 20km/h at the time of the crash, leading to both derailing and considerable damage to their front and right-hand panels.
The driver of the south-bound train and five passengers suffered minor injuries.
Trams on routes 86, 96 and 30 were diverted along La Trobe Street for almost four hours while all west and southbound traffic lanes were closed.
According to the preliminary report, the previous north-bound tram to travel through the intersection before the crash had set the points and turned right onto Victoria Street.
But trams are only meant to turn right into Victoria Parade if travelling on an amended route or being directed to another location.
Trams travelling north along Nicholson Street are presented with traffic signals, as well as primary and secondary points lanterns.
The primary and secondary points lanterns have three lenses, with each lens designed to have an unlit or lit aspect.
But the secondary points lantern's central lens, which can indicate to drivers whether the points are set to the left or right, was non-operational on the day of the crash.
Preliminary crash reports contain no analysis or findings, which will be detailed in the investigation's final report.
Chief Investigator Mark Smallwood said his team would review and examine the operation of both trams, the functioning and operation of their equipment, as well as track infrastructure, signalling, and traffic management systems.
"Investigators will also consider the design and arrangement of infrastructure at the intersection, and the management of safety risk associated with trams deviating from their designated route," he said.
