Two ships broke away from their berths as a thunderstorm roared through Fremantle, causing one to smash into a rail bridge, because the massive vessels had not been prepared for strong winds, an investigation found.
The 190 metre-long car carrier Grand Pioneer was berthed alongside the 140 metre-long cargo ship AAL Fremantle on the night of August 17, 2014 when the storm swept through.
Both broke away from the wharf when a bollard holding stern lines was ripped out.
An Australian Transport Safety Bureau investigation has found high winds caused the Grand Pioneer to move and its vehicle ramp likely hit the bollard, which was made of low quality cast iron.
The ramp was being used to offload cars and eventually fell into the water.
Moments later, the AAL Fremantle struck the bridge - which mainly carries suburban passenger trains - bringing down a stanchion, cutting power to a section of track and also disturbing the track's alignment.
The ship then hit the 65 metre-long fuel tanker Parmelia 1 in the adjacent berth, but that vessel was not damaged.
The ATSB found Fremantle Ports' assessment of risks associated with a ship hitting the bridge after breaking away from a berth was limited, and preventing this happening when the wind was likely to be on the vessel's beam had not been considered.
The safety watchdog also found the Bureau of Meteorology marine forecast title of "strong wind warning" understated the damaging winds expected during the severe thunderstorm, and the forecast did not use recognised marine weather terms for wind speed, such as gale force.
"Fremantle Ports' procedures for adverse weather were not adequate for weather that could be reasonably be expected to occur," the ATSB said.
Despite speculation to the contrary, a meteo-tsunami - which are weather-induced tsunami-like waves - did not contribute to the ships breaking free.
