Five out of Four: The 2015 Alton (England) “The Smiler” Roller Coaster Collision

Max S
18 min readNov 19, 2023


I felt like I had to do something a bit special for the 200th post of this blog, especially since Post #100 came and went pretty much like any other one. And with this blog having covered Maglev-trains, Funiculars and Monorails (those are all early installments, excuse some…”roughness”) a roller coaster isn’t actually that far off from the usual content, having trains, tracks, a block-system and dispatchers. In case you decide to skip the article I’ll use this place to express the most sincere THANK YOU to everyone who’s supported this, at its start, random idea born out of boredom. The blog has been going longer and received more support than I ever imagined. I don’t plan on ending the blog anytime soon, although I may have to space out the installments a little more at some point, which I will announce in due time. To get to the point, THANK YOU for continued support of 200 articles on a blog I started to try and keep my English-proficiency decent. And to those wondering, the blog will return to more conventional railroad-trains next week. So, here we go, article #200:


Alton (Staffordshire) is a town of 1226 people (as of 2011) in central England, located in the West Midlands Region 30km/18.5mi west of Derby and 59km/37mi south of Manchester (both measurements in linear distance).

The location of Alton in Europe.

The town sits adjacent to Alton Towers Resort, an amusement park and resort located on the former site of the Earl of Shrewsbury’s private mansion. The estate opened to the public in 1860 and started installing attractions to attract visitors by 1970 before being officially turned into a theme park on the 4th of April 1980, inspired by the Disneyland-park in Florida (USA). During the 2015 season the park offered 9 roller coasters among its attractions. It’s been confirmed to be the United Kingdom’s leading amusement park with 1.8 million visitors per season (March-November).

The location of “The Smiler” in the western part of the park, captured in 2017. Admittedly, the black track is a little hard to see on aerial photos.

The Attraction Involved

“The Smiler” is an all-steel roller coaster opening at Alton Towers in May 2013. It’s the world’s first “Infinity Coaster”, a high-capacity version of the “Eurofighter”-model offered by the German company Gerstlauer Amusement Rides GmbH. The coaster cost the park an estimated 18 Million Pounds (25.5 Million GBP/29.3 Million Euros/31.5 Million USD in 2023), excluding construction. Gerstlauer sells the roller coaster as an off the shelf layout referred to as “Infinity Coaster 1170”, referring to its track-length of 1170m/3839ft. The layout of the track sees the trains navigate a world-record setting 14 inversions (elements were passengers are turned upside down) at speeds of up to 85kph/53mph. The layout contains two so-called lift hills, inclined sections of track the train is pulled up with a large chain in the center of the track, automatically separating from the chain at the highest point and descending. This is how traditional roller coasters gain the speed required to navigate the layout. The first of the two lift hills on The Smiler is a conventionally inclined lift hill while the second one pulls the trains up a vertical section of track, making passengers essentially lie on their backs.

Each train consists of 4 cars with a single four-seat row in each car for a capacity of 16 passengers per train. The weight of a train has not been published, but people with experience in the industry estimate it at approximately 3 metric tons, empty. Passengers are secured by U-shaped steel restrains covered in plastic which fold down over their shoulders, locking in place. This limits unintended movement by the upper body as forces from various directions pull on the passengers’ bodies.

A photo of a train for The Smiler, published by Alton Towers upon the train’s delivery to the park.

The roller coaster’s pre-opening marketing followed a tradition at the park, with the marketing department announcing project “SW7” (“Secret Weapon 7") in April 2012, as they had done with other roller coasters previously (SW7 making it the seventh “Secret Weapon”). The roller coaster’s actual name, which was confirmed in January 2013 after having been found on leaked trademark filings, refers to a fictional machine called the “Marmaliser” which, operated by a fictional research organization, uses various means to force more happiness in the world as people who undergo “treatment” (ride the roller coaster) will smile whether want it or not. The “Marmaliser” was realized as a large five-legged structure containing various theming-elements and video screens supposedly aiding in the process of achieving the permanent smiles intended for the “subjects” (passengers) as the roller coaster moves through, around and over it.

The silver “Marmaliser” at the center of the black coaster, carrying various theming-elements (yellow). A train can be seen in the background, navigating an inversion.

The roller coaster finally opened with delays on the 31st of May 2013 and usually runs 4 out of its 5 trains, giving it a theoretical capacity of 1200 passengers per hour.

The majority of the attraction as it stood ahead of the accident.

The Accident

The 2nd of June 2015 saw The Smiler operate four of its trains on a crowded day in dry but windy weather, with wind speeds at the site reaching 74kph/46mph. The employees operating the roller coaster (alternatively referred to as the ride crew) plan to add the fifth train to the operation in order to cut down on wait times when, at 1:08pm, the roller coaster’s safety system reports a fault. The dispatcher (head of the ride crew) calls two maintenance engineers to the roller coaster as passengers wait in a train at the station, unable to depart as the fault caused the safety system automatically stop dispatches. The fault is determined to stem from a ride crew member holding the “clear to start”-button on his console down for too long, and is entered into the logbook as such. Passengers from the waiting train are unloaded back onto the platform by 1:10pm while train five, situated on a parallel storage track, is moved closer to the station in anticipation of its addition to the operational fleet.

A spare train sits on the storage track, integrating it into the operation requires the entire section the foreground to be moved over to it.

The unloaded train departs the station at 1:13pm, followed by all four operational trains being unloaded and cycled until, by 1:19pm, all four trains in use are sitting in the station, empty. The attraction’s control system is set to maintenance-mode to allow train five to be transferred onto the actual track of the roller coaster, where it joins the queue of empty trains by 1:25pm.

Operations restart at 1:29pm, with an empty train being dispatched for testing. The train fails to engage with the chain of the second lift hill, which triggers an alert by the safety system as the stationary train did not clear the block section as intended. The Smiler, like most modern roller coasters, uses a block system not too different from the one utilized by railways to ensure safe operation with more than one train. A block section on a roller coaster is a section of track which only one train may occupy at any time, with a measure in place to stop a train if the following section is still occupied. On a railway the train would pass a red signal (if the driver doesn’t see the signal and stop), causing the brakes to be applied. But since conventional roller coaster trains don’t have brakes (or a driver for that matter) the stopping is achieved through elements built into the track. A block section either ends at the top of a lifthill, meaning the train stops by the chain of the lift hill being stopped, or brakes attached to the track stop a train.

A brake at the end of a block section on a similar roller coaster, seen in an on-ride video. This one would stop the train by clamping down on a fin on the underside of the train. The catwalks are used for emergency access.

The 1:29am train ended up at the base of the second lift hill, keeping Block 3 occupied. Witnesses watch as 4 maintenance engineers assemble on the roller coaster’s platform, with three heading out to the position of the train while the fourth engineer heads to the control room. Once reaching the stranded train the three workers push it forward by hand, managing to make it engage with the lift hill’s chain before they return to the control room. The train makes its way around the layout without further incidents and arrives at the back of the station by 1:40pm, creating a queue of five empty trains. The train at the head of the row, referred to as Train 3 by Alton Towers, is dispatched from the station (Block 1) empty. It is pulled up the first lifthill (Block 2), crests the highest point and is allowed to drop down into Block 3, which makes up most of the layout.

The train races across the east-to-west expansion of the layout, passing both the storage/maintenance building and the station with the control room before entering a so-called “Batwing”, the track-element making up inversions 5 and 6 of the layout. The Batwing consists of two half-corkscrews, connected by half-loops. The first corkscrew turns the train upside down during a 90° turn before the half-loop turns it upright, only to then be turned upside down again by the following half-loop, being released into the second half-corkscrew, turning it right side up and by 90° to the left or right again, leaving the element in the direction from which it entered. The small upright section between the half-loops is referred to as the “Apex” of the Element.

A “Batwing”-element on a different roller coaster, with the “Apex” marked in blue.

Please Note: This article originally referred to a “Cobra Roll”-element, which is similar to the Batwing, located close to it and is listed in the official report. After reader input, examining photos and timing the train’s way through the layout I came to the conclusion that the element in question is the Batwing, not the Cobra Roll. I apologize for the Error.

Back at the station the passengers who had waited on the platform since 1:10pm are allowed to board the next train in line at 1:41pm, taking their seats in Train 4. The empty Train 3 has navigated the first half of the Batwing but fails to complete the second half, turning partially upside down at the highest point of the second loop before running out of momentum and rolling back into the section between the corkscrews, referred to as the “Apex” (see above photo). The train rolls back to the top of the first half-loop, then forward again, and pendulums back and forth for a short time before it comes to a stop at the center of the apex. This occurrence is referred to as “valleying”, as roller coaster trains with insufficient momentum will end up in the valley between two higher points.

The safety system, recognizing that Train 3 has failed to clear block 3 by reaching the final brakes ahead of the station, stops the loaded Train 4 at the top of the first lift hill, prohibiting it from entering the occupied block section ahead. An error message pops up at the control room instead, reporting a “Block stop fault” and giving train locations as “4 vehicles ground level 1 vehicle top of lift 1”. This condition is referred to as a “ride breakdown”, as normal operation of the roller coaster has now stopped.

One of the maintenance engineers (the report differentiates people by name, but the names were blacked out for publishing, making them difficult to tell apart) heads out to a remote control panel (labelled OPB 3) near the bottom of the second lift hill. This places him across the layout from the Batwing, over 75m/248ft linear distance away. He uses the control panel to reset the block system, placing the roller coaster in maintenance mode in the process, before heading back to the control room. Train 4 on the lift hill and the trains 1, 2 and 5 at the station are still kept in place at this point, but the error-message goes away. The engineer arrives back at the control room by 1:49pm and asks the dispatcher for a “Code Zero”, the code word for an evacuation via the station.

An aerial photo from the report, marking several important locations around the attraction. Note that the report referred to the “Cobra Roll” while the train actually stalled in the “Batwing” next to it (as explained above). I corrected the label in this photo.

The dispatcher asks the other maintenance engineers present if it’s safe to put the roller coaster in EVAC-Mode at that point, receiving confirmation that it is. A Code Zero usually entails switching the roller coaster’s system from “Maintenance Mode” to “EVAC Mode”, from where it can then be placed back into “Normal Mode”. With confirmation given the “Code Zero” is initiated at 1:50pm, placing the roller coaster in EVAC-mode. The roller coaster’s system automatically selects the train it “senses” to be the furthest along the layout and starts the process of returning it to the station. The train selected is Train 4 at the top of the first lift, which is pulled over the crest of the lift hill and released at 1:51:05pm.

It quickly makes its way to the Batwing, slamming into the back of the stranded Train 3 at 1:51:31pm. Two engineers hear the crash at the Control room and head out to “take a look” at what caused the noise. They notify their superiors of the accident, but records later show that the emergency services weren’t called until 11 minutes after the collision. Eleven of the sixteen passengers are injured to a degree requiring medical attention, five of which are severely injured with two having to undergo leg amputations in the days following the accident.

Workers had to construct scaffolding to let responders reach the crashed trains.


Arriving ambulance crews struggled to reach the crashed trains, which sat on a piece of track about 7m/24ft off the ground, with the whole coaster being constructed in a large fenced off concrete pit due to height restrictions above ground level which made the rescue even more difficult. First aid was rendered once medical responders managed to reach the trains on ladders while Alton Towers’ maintenance crew built scaffolding to ease access and rescue a little bit.

One of the initial responders later described a horrific scene and mentioned the difficulty of tending to a patient several feet off the ground, sitting strongly leaned to one side and with a massive, locked over the shoulder restraint prohibiting access to or movement of most of the upper body. The passengers in the popular front row also had their legs trapped as a metal shield at the front of the car had folded inwards during the collision, trapping and severely injuring passengers’ legs. It took over four hours to cut the final front row passenger, a 17 years old teenager, from the train and get her into an ambulance, as even the fire department’s cutting tools struggled to get through the steel beams making up much of the roller coaster car, including the restraints. The medics who treated her at the site later compared it to a miracle that she “only” lost a leg rather than dying from her injuries right there on the roller coaster as they fought to get her freed.

A photo from the report showing the severely damaged leading car of Train 4 at a storage facility. NOTE: The red straps are from the car’s recovery, the stains are dirt and not blood.

The park closed and was cleared of guests right after the accident, as investigators descended on the scene while the rescue effort was still underway. The rarity of a roller coaster accident this severe also gave rise to a lot of rumors and false information, some of which making it all the way to being aired on TV, further spreading, in honest and simplified terms, nonsense. The question remained though, how could a roller coaster with a state of the art safety system have two trains crash into each other, especially out on the track where trains are meant to be moving at speed?

In contrast to what the media reported at times there was no train which “departed on its own”, or a bug in the control system “applying the brakes of a train at a random point”. And neither was there a planned attack. The further investigators dug into the accident and the events leading up to it the clearer it became that the cause lay entirely within the field of negligence. The “original error” which caused the chain-reaction that led to the accident was the decision by Alton Towers to operate the roller coaster during 74kph/46mph winds due to the high number of guests in the park, ignoring the 55kph/34mph wind speed limit imposed by Gerstlauer above which operation of The Smiler should have been stopped entirely. There obviously wouldn’t have been an accident if the park had shut down the coaster due to high winds, as they were supposed to.

Firefighters use a ladder truck as a crane to access the site of the accident, located within a fenced-in pit.

The ride crew also chose to further go against Gerstlauer’s instructions to shut down the roller coaster by adding the fifth train to the day’s operations in order to maximize capacity, and, throughout the following events, proceeded to fail to inform the maintenance crew that they did. Instructions also dictate that a “test train” (an empty train being sent around the layout ahead of passengers being loaded) should be loaded with water-filled dummies to simulate the weight of passengers, which, especially in high-wind conditions, can make an important difference in the behavior of the train. This also wasn’t done. The excessive wind speed, which was outside the roller coaster’s official limits, was declared the most likely reason why Train 3 valleyed at the Batwing, being unable to maintain sufficient speed to complete the element. The lack of weight from the required dummies is considered a contributing factor, but it’s not stated outright if a loaded train would’ve made it through the Batwing.

The roller coaster was thus left with 3 trains in the station, one on the first lift hill, and one out on the track, stranded. The maintenance crew, however, had no knowledge of the latter train, being under the assumption that four trains were operating. They had dealt with an error declaring a stopped train in Block 3 earlier that day, and now the system was saying a train was stopped in Block 3 again. But looking around, they could see all four trains they thought were operational.

The Smiler is fitted with 25 surveillance-cameras, whose footage is displayed in the control room using two 127cm/50in diameter screens above the control panel and two 38cm/15in diameter screens below the ceiling in a different location within the room. This means that anyone in the control room has access to all the surveillance footage at any point. However, employees noted several flaws in the system during the investigation, explaining how the images on the latter two screens were extremely small, making it hard to see detail without getting up from the control desk and walking over to them. The order of the images, of which several are displayed on each screen at once (with the screen-area split up into smaller rectangles), can also be switched around, making it difficult to keep track of what image is from which part of the roller coaster. Furthermore, the positioning of the cameras was deemed to be not ideal, with most of the stranded train ending up hidden behind track support columns located closer to the camera.

A photo from the report, showing surveillance footage of Train 3 going through the apex of the Batwing before valleying. The A-shaped support it’s about to disappear behind ended up hiding most of it from the camera.

The maintenance crew, seeing all trains they expected to see at the station and on the first lift hill respectively, figured that the error was a “Ghost Train”, a software bug they had experienced before caused by a prior error clearing incompletely when being resolved, leading to the safety system declaring an actually clear block section to be occupied because it previously was. They then failed to sufficiently ensure the track actually being clear, likely missing the last (approximate) 1.5 rows of Train 3 on the surveillance screen, before sending a colleague out to the remote control panel to reset the block system.

They acted under the assumption that four trains were in use, but neither checked the tracks to ensure this nor walked over to the adjacent storage building were they would have noticed the absence of the fifth train. Crucially, the investigation found that the two maintenance engineers who conducted the reset of the block-system had never been taught or even witnessed the procedures included in resetting the block system, so they didn’t know that a thorough check of the supposedly occupied section was required. The training of a maintenance engineer, which largely consisted of “shadowing”/accompanying a more experienced engineer, also didn’t require any time spent with handling a ride breakdown. Thus, it’s possible that an engineer is allowed to work (possibly on his own) in a breakdown-situation without any knowledge of how to handle it. Technically (although not said to be the case here) it could be that a whole team of maintenance engineers has never been trained on handling a ride breakdown.

The reset of the block system cleared out all occupancy-notes in the system, effectively “deleting” Train 3, and put the roller coaster in maintenance mode. The system was then manually placed in EVAC-mode, at which point it detected the trains in the station as well as the stopped lift hill which held Train 4. The system couldn’t detect Train 3 as it had valleyed on open track rather than standing on applied brakes or a stopped lift hill. Had the maintenance and/or ride crew spotted the valleyed train they would have next performed a manual recovery of it (removing the train by crane) and likely evacuated passengers from Train 4 down a catwalk along the lift hill due to the time such a recovery takes. Only then would they have been allowed (and ready) to have the system move the remaining trains to the station via EVAC-Mode.

A crane is used to recover the crashed trains car by car, with the arrow pointing out the almost inaccessible location of the wreckage.

The roller coaster’s system did exactly what it supposed to do every step of the way, with EVAC-mode ordering a gradual return of all trains to the station. Due to the improperly performed reset the system operated on the assumption that Train 4 was the only one outside the station and thus intended to bring it back to the station, which on The Smiler is only possible by having it complete the layout as it can’t move backwards to the station from the top of the first lift hill. The system can’t “know” that it’s being operated by two groups of people with insufficient training and lackluster communication. Yet still, the system’s attempt to “recover” Train 4 did become the final piece of the puzzle, as the accident was unavoidable once the train was released from the top of the lift hill it had been stopped on.

The report notes that insufficient crew structuring played a major role in the chain of events which lead to the accident, with the engineers failing to establish a “leader” within their group once the system went into breakdown mode (due to the occupied block section). It also wasn’t common practice to formally establish the number of trains in operation before conducting things like a block system reset, which would be as easy a referencing the day’s logbook entries. The engineers also couldn’t tell the investigators a consistent version of the rules about using maintenance- or EVAC-mode with passengers onboard, and the members of the ride crew couldn’t agree on how many empty test trains had to be cycled before passengers were allowed to board a train, which was due to there being no official number. The minimum was 1, a maximum didn’t exist.

The empty trains sit at the site of the crash, secured by a ratchet strap, ahead of their removal.

Merlin Entertainment, the company who owns Alton Towers, closed three similar roller coasters at other parks after the accident as protocols and procedures underwent evaluation. They eventually reopened them, while the Health and Safety Executive (HSE, the UK’s government agency responsible for workplace health, safety and welfare) served the company a prohibition notice, banning them from reopening The Smiler without express approval of improvements that would make a repeat of the accident impossible. The roller coaster eventually reopened in mid-March 2016, after the HSE approved new guidelines around the operation of the roller coaster and the training of employees, specifically in relation to breakdown handling. The roller coaster, like many others across the world, was also fitted with a wind speed measuring system and will automatically shut down if the manufacturer’s limit is breached.

The HSE ended up prosecuting Merlin Attractions Limited for their wrongdoing, with the company pleading guilty and being sentenced to a fine of 5 Million GBP (6.7 Million GBP/7.74 Million Euros/8.31 Million USD in 2023) on the 27th of September 2016. The two survivors who each lost a leg in the accident announced that they had filed lawsuits against Merlin Attractions Limited in September 2018, with two more survivors announcing plans to do the same. Their lawyers explained that the filing was done due to a three-year period which they had to sue for damages relating to the accident, and that the actual proceedings were still well in the future due to the complexity of the situation. No ride operators or members of the maintenance crew appear to have been put on trial for their role in the accident.

There were demands after the accident that The Smiler shouldn’t reopen, but it did regardless and is still operating as of late 2023. Alton Towers chose to remove various theming-elements and video clips/audio snippets referencing “correction”, though, while the name and most theming-elements remain, as does the logo. It’s worth saying that The Smiler isn’t an “unsafe” roller coaster, it was and is on the modern standard for operational safety, and the changes to the human side of operations should reduce the risk of an accident even further. Roller coaster accidents where someone is hurt (or worse) are extremely rare, which is part of why even the most minor accident tends to grab public attention.

An official photo giving an overview of the roller coaster, published in Spring 2023.


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Max S

Train crash reports and analysis, published weekly.