A passenger train that ploughed into a safety stop at Richmond station in Sydney's north-west in January was travelling at 35km/h just seconds before impact, investigators have found.

After smashing into the buffer shortly before 10am on January 22, the train was propelled backwards about three metres, sending passengers flying before coming to a complete stop.

Many of the 24 passengers on board the Waratah train had risen from their seats as the train entered the station, leaving them unprepared for the force of impact.

There was no announcement nor warning that the train was about to career into the buffer stop at the end of platform two.