The owners of Alton Towers have said the two carriages that crashed on The Smiler ride should never have been on the same part of the track and that “fail-safes” had not worked.
Four riders were hospitalised with serious injuries after the accident on Tuesday, including one who may have lost a leg, according to unconfirmed reports.
They were among 16 people in a carriage of the 53mph rollercoaster when it rammed into a stationary cart sitting on the track after a test run.
Nick Varney, chief executive of Merlin Entertainments, which runs the theme park, told BBC News the two carriages “should not have been on the same piece of track”.
"Technically that should not have happened,” he added.
"The Smiler is a relatively new ride, all rides have teething problems when they open. Guest safety on those sorts of incidents is not really a major issue in the sense that when you're on a rollercoaster car, the car can't come off the track and you are restrained in the seats.
"When you have a glitch and the ride stops, it's not really an issue of safety to the riders.
"What happened yesterday is something that there are other fail-safes for. There are other braking locks that should stop two cars being on the same track, but that didn't work the way it was supposed to."
A spokesperson for Alton Towers said that she did not know whether human error or a computer glitch was at fault and a full investigation involving the Health and Safety Executive was underway.
Ben Richardson, who had been on the ride before the accident, said the first carriage was “completely static” by the time the second cart was at the tip of the ride.
“At that point they could have unloaded the carriage and got people away safely,” he added.
“Whether that was computer error or human error, I don’t know, but common sense would say, get the passengers off while you can.”
Two men aged 27 and 18 and two women aged 19 and 17 were airlifted to hospital with serious leg injuries and the other 12 riders - six men and six women – were treated for less serious injuries.
The theme park remained closed on Wednesday and Mr Varney said he could not say when it would reopen after the “unusual and very tragic accident”.
The best roller coasters in the world
The best roller coasters in the world
1/9 Millennium Force, USA
Breaking six world records when it was built in 2000, Millennium Force at Cedar Point in Ontario, United States, was briefly the tallest and fastest coaster in the world before Steel Dragon 2000. Millennium Force was also the world’s first Giga Coaster, exceeding 300 feet in height. Website: https://www.cedarpoint.com/ Ticket cost: £29.24
2/9 Formula Rossa, Abu Dhabi
Formula One fans looking to experience the thrill of high-speed manoeuvres need look no further than Formula Rossa, currently the world’s fastest roller coaster, located at Ferrari Word in Abu Dhabi, United Arab Emirates. Once strapped in to the Ferrari “Rosso Scuderia” F1 inspired cockpit, riders experience an incredible top speed of 150mph, accompanied by acceleration G-Force of 1.7Gs. In order to accelerate to top speed in under five seconds, the ride uses a hydraulic launch system similar to those used to launch jets from aircraft carriers. The ride is so fast riders are required to wear safety goggles. Website: http://www.ferrariworldabudhabi.com/en-gb.aspx Entry cost: £38.18
3/9 Kingda Ka, USA
Currently the world’s tallest roller coaster, Kingda Ka reaches an impressive height of 456 feet. The roller coaster, found at Six Flags Great Adventure in Jackson, New Jersey, in the United States, used to be the world’s fastest roller coaster, reaching 128 miles per hour in 3.5 seconds, before it lost that record to Formula Rossa in 2010. After a 90° rise to the top, riders then plummet down a 270 ° spiral drop. Website: https://www.sixflags.com/greatadventure Entry cost: £24.54
4/9 Colossos, Germany
The world’s tallest wooden roller coaster, Colossos in Heide Park, Germany, stretches 196 feet into the air. It is constructed using laser cut wood, which means the entire structure snaps together like pieces of Lego. Due to this, the wooden track gives a very smooth ride. Website: http://www.heide-park.de/en/heide-park/ Entry cost: £25.45
5/9 Steel Dragon 2000, Japan
Named after the Chinese New Year in 2000, Steel Dragon 2000 at Nagashima Spa Lad amusement park in Mie Prefecture, Japan, holds the record for the longest roller coaster in the world. Boasting a track length of 8,133 feet, it’s also the sixth fastest coaster in the world. Built in Japan, the coaster needed extra earthquake protection, pushing construction costs over $50 million. Website: http://www.nagashima-onsen.co.jp/index.html/ Ticket cost: £5.74
6/9 Takabisha, Japan
Famous for having a drop angle of 121°, Takabisha, located at the Fuji-Q Highland theme park in Fujiyoshida, Yamanashi, Japan, is the steepest roller coaster in the world. The drop angle is known as a “beyond vertical” drop as riders travel back on themselves as they fly over the vertical lift and down the drop. Website: http://www.fujiq.jp/en/ Ticket cost: 5.74
7/9 Top Thrill Dragster, USA
Before being surpassed by Kingda Ka, Top Thrill Dragster at Cedar Point in Sandusky, Ohio, United States, was the world’s tallest roller coaster. Along with Kingda Ka, Top Thrill Dragster is one of two Strata Coaster types of roller coaster, featuring a drop of 400 feet and a full circuit. Reaching speeds of 120 mph in less than four seconds, Top Thrill Dragster may last only 17 seconds, but it’s sure to thrill. Website: https://www.cedarpoint.com/ Entry cost: £29.18
8/9 Space Mountain, USA
A clear fan favourite, Space Mountain, at Disney World, California, takes visitors on a rocket ride through stars, galaxies and asteroids. The ride is replicated across all five Magic Kingdom-style Disney Parks, so there’s no excuse to miss it. Website: https://disneyland.disney.go.com/ Entry cost: £56.15
This one’s a bit of a cheat because the ride isn’t actually completed yet, but Skyscraper at Orlando’s International Drive is planned to be the world’s tallest roller coaster in the world with a 570 foot tower. Riders will catch an elevator to the top of the structure before following the winding track down at 65 miles per hour. Unfortunately, the ride won’t be completed until 2016, but there’s still plenty of time to get excited.