Eighty-three roses have been thrown onto the tracks at Granville to remember each of the people killed in Australia's worst train disaster, as part of 40th anniversary commemorations of the accident in Sydney.

Survivors, first responders and relatives of the victims of the Granville train disaster have gathered in the western Sydney suburb.

Roses collect on the bridge built to replace the one that collapsed during the accident. ( ABC News: Clare Blumer )

As chimes sounded at 8:10am — the time the train crashed in 1977 — the names of the 83 victims were read out at the Granville memorial wall.

Another 213 people were injured that day when a commuter train derailed near Granville railway station and a bridge collapsed onto the carriages.

After the reading out of victims' names, a church service was held at St Marks Anglican Church followed by a memorial service at the memorial wall.

Then the crowd crossed the bridge that replaced the one that collapsed onto the train, and 83 red roses were dropped onto the tracks — one for each person who died.

NSW Premier Mike Baird and Prime Minister Malcom Turnbull were both in attendance and gave speeches next to the memorial.

The Prime Minister lays a wreath with wife Lucy watching on. ( ABC News: Clare Blumer )

"You are not alone, not today and not then," Mr Turnbull told the crowd.

"Forty years ago, the nation wept with you, shared your horror, admired the courage of the victims, survivors and those who rushed to their aid.

"To those who survived, we offer our heartfelt admiration for the grace and the strength you have shown. Many of you still suffer terribly from the ongoing physical injuries and the emotional scars of your loss.

"While what was lost that day will never heal, lessons were learned, safety regulation was improved, a reminder that the first duty of every government is ensuring the safety of the people and being always vigilant in making it better assured."

Survivors remember 'horrific' day

Sandra Lucre was 23 when she boarded the train at Penrith. She was in the first carriage and received only minor injuries.

"The engine derailed and dragged the first carriage with it," she recounted.

"It was horrific ... I was one of the lucky ones, I walked away.

"I've been very grateful for my life. I was pregnant at the time with my eldest son but I didn't know — he'll be 40 in October — and that got me through, but I've had nightmares on and off and I still do."

Ms Lucre left her home at Sanctuary Point, near Jervis Bay, at 4:00am this morning to make it to Granville for the commemorations.

She said she was "trying to keep it together" during the service.

"I keep thinking back to that day and I can still see what I was wearing, I can still remember the sounds, I did not hear that bridge come down even though it was so close," Ms Lucre said.

"The memories are very vivid, I think even if I got Alzheimer's I would still remember how it felt to have the windows of your carriage shatter, to have the roof lift and the side go.

"It it's not an experience I'd like anyone to live through at all and I feel so sorry for the ones that lost people — it was very sad."

Sandra Lucre said she "suffered many years of guilt" because she survived the disaster. ( ABC News: Philippa McDonald )

Natalie Gordon, whose father was in the fourth carriage of the train, said the day had started out as usual.

"He was travelling to work [from Emu Plains], he worked in the city and it was just a normal day for him, my mum dropped him at the station," she said.

"He was trapped for 10 hours and he was one of the last to be rescued, and then he died three days later in hospital."

Ms Gordon, who was four when her father died, said the accident had a huge impact on her life, but she felt some solace from the commemorations.

"It's a very emotional day, it's a special moment just to be here thinking of him and everyone else who lost their lives on that day," she said.

Natalie Gordon, with her mother Annette, was four when her father Bryan died in the disaster. ( ABC News: Philippa McDonald )

"It's good for everybody to get together who have lost their loved ones as well — I think we all share a special bond — just a time to reflect and remember."

Meredith Knight, who lost her father in the accident when she was a young girl, said the disaster changed the lives of those affected forever.

"The depth of grief and suffering was incomprehensible," she said while speaking at the memorial.

"The adverse repercussions on our ongoing lives [were] multifarious and far-reaching.

"But life goes on. We coped as well as we could and we got on with it."

Meredith Knight, who lost her father in the Granville train disaster, stands beside the Granville memorial wall during the commemorations. ( ABC News: Clare Blumer )

NSW Government to apologise

The NSW Goverment is due to apologise to the families of those in the Granville train disaster in February

At the time, then-New South Wales premier, the late Neville Wran, described the state of the railway system as "ramshackle".

Investigations and inquiries revealed an alarming lack of investment in maintenance and ageing infrastructure and following the disaster, the State Government borrowed heavily to modernise the railway.