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PM marks Granville disaster anniversary

Forty-six years after Australia's worst rail disaster, Prime Minister Anthony Albanese has commemorated the 84 lives lost and paid tribute to those who rescued the more than 200 injured.

"Nearly half a century on, we think of them still," Mr Albanese told a memorial service at the scene of the Granville derailment, in Sydney's west, on Wednesday.

"The years not lived, the dreams not realised and the great promise of those lives unfulfilled."

While softened by time, the grief felt by the families and loved ones left behind hadn't faded, he said.

"We hold them all in our hearts and we carry them with us."

The deadly crash happened when a packed commuter train from Mount Victoria in the Blue Mountains on its way to the city derailed and struck Bold Street bridge near Granville station shortly after 8am on January 18, 1977.

The more than 500-tonne concrete structure, with four cars on deck, collapsed onto the wooden-framed third and fourth carriages of the train, instantly killing at least half their passengers. Some 213 people were left injured.

An 84th victim of the tragedy, an unborn child, was added to the fatality list in 2017.

"We can scarcely imagine what it was like in that awful moment," Mr Albanese said.

"The suddenness of it, the shock of it, the violence and the noise of it. A moment in that bright January sunshine that brought the finality of darkness."

An inquiry found the primary cause of the crash was poor fastening of the track.

Then NSW premier Gladys Berejiklian made a long-awaited apology to survivors, emergency workers and relatives on the 40th anniversary of the disaster in 2017.

Following his speech, Mr Albanese laid a wreath at a memorial wall carrying the names of the victims near the crash site.