A FORENSIC crash investigator has told the second day of the inquest into the Dreamworld tragedy there was 20 critical seconds after the Thunder River Rapids rafts collided and if the emergency stop button was pressed it may have prevented some injuries.

Senior Constable Steven Cornish told Southport Coroner's court the slower stop button, which takes eight seconds to bring the Thunder River Rapids Ride conveyor to a halt, was pressed ten seconds after the incident.

Under cross examination he was asked if the emergency stop button was pressed would it have avoided the tragedy which killed Kate Goodchild, Luke Dorsett, Roozi Araghi and Cindy Low.

"I would not have avoided it," he said.

"It may have limited some injuries. Possibly."

Police examine the scene of the Dreamworld ride tragedy. Photo: Adam Head
Police examine the scene of the Dreamworld ride tragedy. Photo: Adam Head

The first day of the inquest heard the ride operator close to the emergency stop button, which takes two seconds to work, did not know what the button was for and was told not to worry about it.

INSIDE THE DREAMWORLD CORONIAL INQUIRY

Snr Const Cornish today told the court there was ten seconds between the rafts first hitting and the slower emergency stop button being pressed.

The rafts first collided at 2.05.03pm on October 25, 2018 and the conveyor belt on the ride did not come to a complete stop until 2.05.22pm - almost 20 seconds after the first collision.

Forensic crash investigator Senior Constable Steven Cornish. (AAP Image/Glenn Hunt)
Forensic crash investigator Senior Constable Steven Cornish. (AAP Image/Glenn Hunt)

He said based on how long it took for the ride to slow, it appeared the slower emergency stop button was pressed.

The inquest into the Dreamworld tragedy is underway.
The inquest into the Dreamworld tragedy is underway.

DREAMWORLD STAFF'S SAFETY FEARS REVEALED