Alton Towers operator Merlin was at fault for the Smiler rollercoaster crash, a court has heard.
Two teenagers were left needing leg amputations and several other victims suffered serious injuries in the accident in June 2015.
An investigation found human error caused the crash, which saw a carriage smash into an empty car.
Operator Merlin Attractions has been warned to expect a “very large fine” for health and safety breaches.
Opening the sentencing hearing at Stafford Crown Court, barrister Bernard Thorogood, prosecuting for the Health and Safety Executive (HSE), said the crash equated to “a family car of 1.5 tons having collided at about 90mph”.
•The £18m Smiler was the world’s first 14 multi-loop rollercoaster with up to five trains running at any one time
•On 2 June four trains were operating on the ride; a fifth was stored away
•At 13:00 BST there was a problem with one of the trains; technical staff were called
•One of the engineers thought it was a good opportunity to add the fifth train because the park was busy
•An empty test train was sent but failed
•Engineers pushed the train until it engaged with the system and off it went
•Another empty train was sent out. It got stuck, too, but in a different place
•Engineers were unaware of this, thought everything was working fine and handed it back to operators
•The train with 16 passengers on was sent out and stopped
•The engineers looked but could not see the stalled car, thought the computer was wrong, and over-rode the stop. This set the 16-passenger train in motion and into the empty carriage
He said a test carriage had been sent around the 14-loop ride but had failed.
‘Fault with employers’
Engineers re-set the ride and overrode a computer system “block-stop” which they believed had halted the ride in error, sending a full 16-seater rollercoaster car around the track and into the empty carriage.
Mr Thorogood said that the “fault here is with the employers”, not individuals.
He said the engineers were “without guidance from above”, and had not been given a system to follow to safely deal with the problem on the track.
“The fault is with the defendant for not devising a scheme, for not guiding the work of the engineers,” he said.
Among those who attended the first day were Victoria Balch and Leah Washington, who had legs amputated after the crash.
The court heard how there were estimated winds on the day of 45mph. But the manufacturer’s manual said the ride should not be operated at speeds above 34 mph.
Mr Thorogood said the victims were left for a “significant period of time” at least 20ft (6m) above ground, waiting for medical attention because of the inaccessibility of the ride.
He said engineers on the day had not read or seen the operating instructions for the ride.
The Recorder of Stafford, Judge Michael Chambers QC, is set to hear mitigation from Merlin, based in Poole, Dorset, before passing sentence.
In April the operator admitted charges of breaching the Health and Safety Act. An investigation by the park found staff misunderstood a shutdown message and wrongly restarted the ride.
Since the crash, a number of safety changes have been made including improved access and a policy of closing the ride when winds exceed 35mph.