Cautionary Tales with Tim Harford - The Thrill and the Drop: A First Date Rollercoaster

Episode Date: February 14, 2025

Leah Washington and her new boyfriend Joe Pugh are on their first day out together. They're at Alton Towers theme park, where they've chosen to ride the "Smiler" rollercoaster: a terrifying tangle of track that loops and swoops through a world-record 14 inversions. Leah and Joe are seated right at the front of the train and, as they reach the highest point of the ride, they steel themselves for the drop. But then, quite suddenly, the ride stops. Down on the ground, the computer system that controls the rollercoaster is warning that another carriage is out on the track, right in the path of Leah and Joe's train. The engineers are certain the computer is wrong... Algorithms are often faster and cleverer than humans, and they can help us avoid accidents. But computers can make mistakes. When should we trust our own heads, instead of the machine? For a full list of sources, see the show notes at timharford.com.See omnystudio.com/listener for privacy information.

Pushkin You might have noticed that things are a little different on Cautionary Tales this year. In 2024 we brought you a new episode every fortnight. But this year we are doubling our output. New stories of heart-thumping peril, mind-blowing mistakes and jaw-dropping scandal will now be delivered straight to your ears every week. Here's one for you right now. Not so very long ago I took my son with me to an amusement park to celebrate his 12th birthday. He's obsessed with roller coasters, although usually he just experiences them

through the medium of YouTube. It's one thing to see the footage someone took from the front seat, to actually be there, it's a different thing. Riding a roller coaster is a strange kind of fun. You're volunteering to be terrified for the sake of entertainment. And the roller coaster we'd come to ride certainly leans into that idea. It's called the Smiler. The conceit behind the Smiler is that people who aren't smiling enough will have their lack of a smile corrected by a strange Orwellian institution called the Ministry of Joy. The smiler's logo is a ghastly grin connecting two hypnotically spiralling eyes.

And so we went to Alton Towers in England to ride the Smiler. The ride doesn't soar in the high curves of a classic roller coaster. Instead, it's an impenetrable looking spaghetti tangle of black and yellow, with the knots and curls of the roller coaster track intersecting with a huge five-legged structure, some kind of diabolical machine decorated with a wraparound screen displaying dystopian messages and unsettling graphics. It's hard to figure out what goes where.

As we waited in line, underneath the belly of the thing, we gazed up at the tortuous coils of the ride through black netting. That added to the vibe of a correctional facility that was really to protect us from wallets and phones falling out of the pockets of the riders in the trains above. And those trains looped and swooped around and around above us, two together on different parts of the track, diving and rolling around each other like mating birds. But there was no bird song. The sound was deafening. A nightmarish theme tune like a nursery rhyme from hell.

The steel roaring as the trains rush overhead, so close that it seemed we could touch them. And of course, there were the screams of the riders. They screamed and they screamed and they screamed as the ride turned them upside down over and over and over again. A world record. Fourteen inversions. And as we gazed upon the sheer awfulness of the thing, my son turned to me and said, My son turned to me and said, Dad, I'm not sure I want to go on this ride. And he told me something else.

Dad, he said, you should do a cautionary tale about the Smiler. I'm Tim Harford, and this is that cautionary tale. at Portionery Town. 17-year-old Leah Washington's first big day out with her new boyfriend, Joe Pugh, was a trip to Alton Towers, the theme park which is home to the Smiler. Leah suggested going on the Sonic Spinball coaster. Joe wasn't convinced. Why line up for hours when the ride isn't even that good? It was June 2015. The Smiler itself was only a couple of years old, but had quickly become an iconic roller coaster ride, so Joe suggested the Smiler instead. Now that is a roller coaster worth waiting for. Leo was nervous, she'd never been on the Smiler, and it looks terrifying. But she agreed, and so they patiently lined up, edging

forward to enjoy their turn. It was a windy day, but they were sheltered from the worst of the gusts as the rollercoaster cars swooped and screamed above them. The line edged forward and the minutes ticked past. Half past eleven, noon, half past 12. By one o'clock, Leah and Joe could see they were close to getting onto the Smiler itself, with the diabolical nursery tune playing and the lines surrounded by unsettling images of compliant, grinning faces. So we queued for a good hour and a half, Leah later recalled.

And then we got to the front, and they put us on the front carriage. Those words are from a television interview she gave just a couple of months later. In the interview, Leah is serious, but calm. She's a remarkably self-possessed young woman. She's also missing her left leg. Smiler trains are short and wide. Four rows, four seats in each one. Leah and Joe were in the front row. Me and Joe got excited being at the front. The front row is much sought after. You get the best views, the most excitement, the most direct exposure to everything the Smiler has

to offer. But then we sat down, put the safety bars down, then we were sat for five, ten minutes, and then we had to get back off because there were technical difficulties. That was a bit frustrating, but was Leah worried? No. Not really, because all rides break down at some point, but you didn't expect anything bad to happen. So Leah and Joe stood at the front of the line and waited to get back on. The Alton Towers theme park has dedicated teams of engineers. The park wants to keep the rides running smoothly and safely with a minimum of interruptions. The need for safety is obvious enough, but

so is the need to minimise downtime. There can easily be 2,000 people in the line to ride the Smiler, and Alton Towers doesn't want people saying, I queued for two hours for the Smiler and I never even got a ride. The show must go on. Which might explain why, on the 2nd June 2015, the Smiler was operating despite the windy weather. When the roller coaster registered a fault, and Lear and the other riders were taken off the train and asked to wait, two teams of engineers hurried to the scene. The line was only getting longer, and two trains were sitting out on the twisting roller coaster track full of increasingly anxious passengers, wondering what the problem was,

and whether it was anything to do with the gusts of wind. The first team of engineers started to diagnose the problem, which was nothing serious, and also decided to add a fifth train to the track while the ride was suspended. That meant that once the roller coaster was operating again, it would accommodate a few more passengers. Seven minutes after the fault appeared, the engineers were able to bring a train of relieved guests back to the station, where they got off and wandered away to enjoy the rest of the theme park. A minute after that, another train, the last occupied train, arrived, and the passengers

disembarked. Now all four empty trains were safely inside the roller coaster station and the fifth train was added. This took another five minutes, while Leah and Joe and 2,000 people behind them waited and wondered what was happening. As the fifth train was being added, the roller coaster's electronic system flashed up seven more fault codes. Each of them was minor, but each of them needed to be acknowledged, checked and then cleared. By now, Leah and Joe and the others had been waiting nearly 20 minutes to get back on the ride, and the engineers sent an empty train around the roller coaster just to check that

everything was working properly. It wasn't. The train went out, but it didn't come back. Like many roller coasters, the Smiler operates on a combination of gravity and momentum. The trains don't have engines in them. Instead, each train is pulled up a long slope by a chain lift, then released to run the course of humps and loops until

finally coasting back into the station. Roller. Coaster. The clue's in the name. But because the Smiler has that world record tangle of 14 inversions, and because it stays fairly low, levelled with the treetops, one chain lift hill won't do the job. And so, halfway round the ride comes one of the defining moments of the Smiler experience. There's a second chain lift. And instead of being pulled up a long slope, the chain runs vertically. Suddenly your seat tips back so far that your feet are higher than your head, and you stare directly up at the sky, being hoisted higher and higher up a vertical track. But in June 2015, that test train didn't come back because it didn't quite reach the second lift, the vertical one.

It coasted to a halt just short of where the lift chain would engage. Why? Unclear. The fact that it had no passengers meant that it would have been a little lighter, and carried less momentum. Then there were those gusts of wind. Whatever the reason, it wasn't quite close enough for the lift chain to finish the journey. As they were puzzling over this problem, the first team of engineers were joined by the second team, a pair of electrical engineers. They all huddled together for a brief conference, but one thing

that doesn't seem to have been mentioned was that a fifth train had been added to the track. Anyway, it wasn't hard to figure out what was wrong. The ride had sensors which showed that a section of track was occupied by a train. That train they'd just sent out as a test. The engineers could also look at CCTV images and see that train, stopped just shy of the chain lift. Three of the engineers made their way down to the track's halfway point, the bottom of the vertical lift hill. They put their shoulders to the heavy train and started to push until the train clicked into the chain lift and up it went, straight up the

vertical rails before coasting around the remaining loops and corkscrews and back to the station. Leah and Joe and the rest of the 16 passengers had been waiting for half an hour since being put onto a train and then taken off again, with no knowledge of what the Smiler engineers had been up to. But at long last, they were nearly ready to get the passengers back onto the ride. Ahead of the train Leah and the others would board, there was another empty train. The engineers sent it off around the circuit and Leah and Joe stepped forward to be strapped into the front row of the Smiler, ready for the ride of a lifetime. The cautionary tales will be back after the break. Roller coasters are safer than lots of things people do for fun. They're certainly a lot safer than riding in a car. If you believe the numbers from the International Association

of Amusement Parks and Attractions, and why wouldn't you believe them, my son and I ran about the same risk in driving 100 miles to Alton Towers and 100 miles back again that we would have faced if we'd ridden 600 roller coasters. So sure, roller coasters are pretty safe. But they don't feel safe. They're not meant to feel safe. And if you pushed a nervous roller coaster rider to think about what might actually be dangerous about a roller coaster, they'd probably tell you two things. First, I might fall out of my seat. And second, the entire train might fall off the track. That makes intuitive sense. The tracks look narrow and exposed. And the trains go fast, take perilous curves, and for goodness sake they go upside down.

But that's not really the problem. Here are the words of Stephen Flanagan, an expert on roller coaster safety. Although the public perception of the hazards associated with roller coasters may be focused in the danger of a train parting company with the track. In reality, the bigger and more difficult to resolve issue has always been the hazard of trains colliding on the track. When you get on a roller coaster like the Smiler, you really don't need to worry that the train is going to fall off one of those gravity defying loops. You really don't need to worry about anything, but if you did feel like worrying about something, I'd suggest worrying that your train might

smash into another train. As Leah and Joe's train moved off, a diabolic voice boomed over the speakers. Join us! Then the train plunged into a dark section of track, shocking the passengers by flipping upside down and right side up again before emerging into daylight and slowly clanking up the first chain lift, higher and higher and higher. Ahead of them, on the Smiler tracks, was an empty train. And none of the passengers realized

that empty train was slowing as it approached the top of a loop. The wind was still gusting, the empty trains were still a little on the light side. The train came to a stop, then slowly rolled back to settle in a dip. Once Leah and Joe's train was released from the lift hill, it would take 26 seconds to loop over to that dip.

They were less than half a minute from disaster. Except their train just stopped right at the top of the lift. We got to the first lift hill, and it got stuck at the top, so obviously me and Joe were discussing, oh, this isn't right. Why had the train stopped? Simple. Although the Smiler engineers hadn't realised there was a problem, the Smiler's monitoring system knew perfectly well that there was a train stalled out on the track. Automatically it held Leah and Joe's train at the top of the slope, the highest point of the Smiler, waiting for the blockage to be cleared. Catastrophe had been averted by an automated system.

So now what? Paul Meehl was an expert who became fascinated by the mistakes experts make. That was partly an intellectual interest of his, but it was also very personal. In 1935, when Meehl was 15 years old, his mother had gone to her doctor with some symptoms which the doctor attributed to problems with her inner ear. In fact, the cause was a brain tumour. The doctor could have diagnosed the tumour by asking some basic questions and performing some basic checks, but didn't. A year later, the tumour had grown and spread. It was finally diagnosed by a different doctor, and Paul Meehl's mother died soon after.

Meehl later wrote, This episode of gross medical bungling Permanently immunise me from the childlike faith in physician's omniscience That one finds among most persons. Meehl became an academic researcher and a clinical psychologist, And he never lost his curiosity about the fallibility of human experts. In his early thirtiess he published a book that was to become famous, Clinical vs Statistical Prediction. The book asked the question, should you trust the judgement of an expert doctor? Or is it better to take a short list of symptoms,

feed them into a simple flow chart, and do whatever the flow chart says. Such a flow chart might have saved his mother. This was 1954, so we're not talking about pitting human experts against sophisticated artificial intelligence. We're talking about pitting human experts against a crude formulaic process. But Meehl found that the crude formulaic process often beat the humans. Three years later, he published an academic article with a punchy follow-up question. When shall we use our heads instead of the formula? It's a question that's much more pressing today than it was when he asked it in the

1950s. Computers tell managers who to hire and who to fire. They tell radiologists whether a shadow on a scan is cancer or not. They advise judges on who should be released on bail and who should be detained. And they helped social services prioritise calls about children at risk. The computers are everywhere. So when should we trust them instead of our own judgement? Paul Meehl wrote, I find the two extreme answers to this question, namely always and never, equally unacceptable. At Alton Towers, the engineers were about to override the computer. That's not always

the wrong choice. Sometimes the human is right and the computer is wrong. Unfortunately, this wasn't one of those times. Leah and Joe and the others had waited an hour and a half to get onto the Smiler, then another half an hour while the technical fault was resolved. Now they were perched precariously at the highest point of the ride. A long minute ticked by. Then another. Excitement gave way to waves of anxiety, boredom and annoyance. They set over the tannoy. They really weren't supposed to be poised and ready to roll for such a long time. What was going on? The Smiler's engineers were trying to figure that out too.

The Smiler has a simple computer system designed to prevent trains from smashing into each other. At certain points on the track, there are proximity switches which register when a train enters a block of track and when it leaves it again. If the system thinks a train is on a particular block of track, it will automatically prevent the train behind it from being released into that block. That's what was happening here of course. The empty train hadn't left the block, in fact it was still gently penduluming backwards and forwards, settling in the valley ahead of

Leah and Jo's train. So the Smiler's computer prevented the occupied train behind it from moving forward, leaving Leah and the other passengers waiting and waiting at the top of the lift hill. Meanwhile, on the ride's control panel, the Zone Stop alarm was activated, notifying the engineers that one train was being held because the train ahead hadn't left its block of track. Hmm. Well. The occupied block was the one including the vertical chain lift, where the previous train had stalled, it was natural to assume that if a second train had stalled, that would be where it was. One of the engineers went out to have a look.

But there was no train at the bottom of the vertical lift. As far as he was concerned then, the Smiler's collision prevention system was just malfunctioning. Probably it hadn't reset itself from the train which stalled 15 minutes before. Now that might seem like a big assumption, but this was one of the engineers who derived after the fifth train had been added. He didn't know about it, or if someone had mentioned it, it had slipped his mind. So he thought there were four trains, and he knew where four trains were. Blias at the top of the lift hill, and three in the station. If he turned to look over his shoulder, and looked carefully, he might have seen the fifth

train, valed at the other end of the ride, through the tangle of rollercoaster track. But he didn't look. Or if he did, he didn't see. At the bottom of the vertical chain lift was a control panel to reset the block sensors. The engineer performed that reset, telling the computer to forget its erroneous belief that there was a train stuck on the track. Unfortunately, it wasn't the computer which had an erroneous belief. It was the humans. The missionary tales will return in a moment. Leah's train has now been held at the top of the chain hill for six long minutes. There's still a chance. The Smiler system won't release the train without an explicit override from the humans. So now the critical decision is with the engineers back in the station.

But they don't explicitly discuss whether there are four trains running or five. They don't send anyone out to visually confirm that the whole track is clear. Nor, it seems, do they look carefully at the CCTV screens. The Smiler does have lots of CCTV screens, very on brand for a dystopian roller coaster experience. But the ride is such a tangle of track that it's hard to see clearly. Right now, the valid train is partly obscured, and the engineers don't look carefully enough. Maybe they don't look at all. They're all just assuming the computer must be wrong. So they decide to override it.

The Smiler's system still won't release one train into a section where it knows another train is stationary. But it doesn't know about the stationary train anymore because its memory of the obstacle has been deliberately reset. Leah recalled, it just set back off without any warning. At last, Leah's train starts to roll down from the lift hill and accelerate into loop after loop after loop. 26 seconds away is a stationary train. It were fine. We were going around, loops and everything, and we

just came round this corner and I saw this car and I'm like, oh my god, this isn't good. Paul Meehl, the clinical psychologist who posed the question about when we should follow the formula and when we should use our heads, didn't have an easy answer. But he did suggest a rule of thumb. If you as the human know something that the algorithm doesn't know, that the algorithm can't know, that's a reason to think about overruling the computer. But when investigators later looked into the causes of the Smiler accident, they noticed that the engineers had a patchy knowledge about how the rides' fault alarms actually worked.

This meant they were often puzzled when the alarms went off. They'd do some safety checks and reset the system, but exactly why the alarm had sounded was sometimes a mystery. So the engineers regarded the alarm system as capricious and unreliable. If the engineers had been better trained, they'd have understood the logic of the alarm system and would have been able to think clearly about when to override it and when not to. Paul Meehl warned us, if you're going to overrule the computer, you'd better have a reason to think

you know something that it doesn't. But to do that, you need to have a firm understanding of how the computer works. The Smilers engineers didn't. As Leah and Joe and the others looped upside down and saw the empty train ahead of them, they had only a moment to brace for the shattering impact. The train wasn't going especially fast. You'd probably walk away from a car crash at that speed. But unlike cars, roller coasters don't have crumple zones. Leah was right at the front with no protection. And as metal smashed into metal,

the two trains locked together and rocked backwards and forwards 12 times with the legs of the front row passengers crushed between them. The next thing I remember was the screaming, and the blood, there was so much of it. The metal of the safety bars had folded into our bodies, said Leah later.

All I wanted was to hold Joe's hand, but when I looked down at it, I could see there was no way I could. His little finger was hanging off his left hand, and the middle finger on the other was broken. All the front row passengers had horrendous leg wounds. Both Joe's kneecaps were shattered. Leah's injuries were even worse.

I started getting pain. I couldn't feel my toes, Leah remembered. And I started to look at my legs. My left leg was all pushed up. They were snarled up in a tangle of metal at a 45-degree angle, 20 feet above the ground. And the Smiler operators were apparently still confused because it took 17 minutes before anybody called for the emergency services.

Up on the coaster, Leah nearly died from blood loss, but an air ambulance flew in blood for an emergency transfusion 20 feet above ground. Later, she stopped breathing. But the medics, reaching her from precarious ladders and hoists, managed to resuscitate her. Once she was released from the train, hours later, Leah was flown to hospital, slipping in and out of consciousness. She woke up 24 hours later. I realised two things were missing. My boyfriend and my entire left leg.

The doctors told her sorrowfully that they'd faced a choice. Her leg or her life. So they took the leg. The woman sitting next to her on the rollercoaster, Vicky Bolch, also had her leg amputated. Joe Pugh was elsewhere in the hospital. He and several other passengers also suffered severe injuries. All because the Smiler's engineers hadn't

double-checked when the computer told them there was a train out on the track. Given what she's been through, Leah Washington is doing incredibly well. She's something of an Instagram influencer, posting videos of herself learning to walk, learning to run, learning to ski, or selfies of her looking fabulous in a bikini. They look like a lot of Instagram selfies in fact, except that she's looking fabulous in a bikini with an artificial leg. Joe never regained the use of one finger, but his knees recovered eventually, and the pair are still together. Leah is now Mrs Washington Pugh, after she and Joe tied the knot in 2024. But that happy ever after ending so nearly didn't happen. At that moment, when Leah was unconscious and trapped in crumpled metal 20 feet above

the ground, when a team of paramedics on hoists were trying to get her breathing started again, it was touch and go. The medics later told her if the weather had been any colder she wouldn't have made it. In a world where we're surrounded by automatic systems, statistical formulas, algorithms and computers, we're going to have to get better at deciding when to trust them and when to overrule them. There will never be a hard and fast rule for when to do that, but if you're thinking of ignoring the computer, it's wise to have a logical reason to think you know better. The Smiler engineers

didn't. When investigators picked over the disaster, they concluded that there was nothing wrong with the roller coaster itself, nor with the automatic alarm system. It was modern, well designed and functioned exactly as intended. The problems emerged from the working practices of the engineering team. It was partly the fact that the engineers didn't fully understand their own safety alarms. And it was also that nobody in particular was in charge of the process of resetting

the Smiler after the very first fault alarm. There were the ride operators, the first engineering team, and the second engineering team, all trying to make decisions. There were loose, informal conversations in which nobody had a full overview of what was going on. There was no written process for working systematically through a checklist before resetting the ride. And there was no formal assignment of responsibility

as to who had the authority to override the automatic system and under what circumstances. This lack of a formal process was critical. Without it, the engineering team could just assume that the track was critical. Without it, the engineering team could just assume that the track was clear. With a formal process, someone would have been clearly responsible for checking. Fifteen months after the accident, a judge called it an obvious shambles involving lack of communication and double checking,

shambles involving lack of communication and double checking, which could and should easily have been avoided by a written system of working, including a single overall supervisor. Automatic systems can help us avoid accidents and make better decisions, But Paul Meehl's question will never go away. When should we use our heads instead? Maybe the trick is in the question. It's OK to use your head if you really are thinking. Very often, we aren't. As I waited in line for the smiler with my 12-year-old son, snaking through the maze of concrete under the black netting,

it was hard not to think about Leah Washington and her accident. Maybe all this was going through my son's mind too, as the queue edged forward and his knees buckled. I'm not sure I want to do this. Come on, I said. You came all this way. You'll be sad if you don't do it.

So we did it. And it was amazing. We had a great time. And he was so proud of himself. But there was one moment when we got to the front of the line, when we were offered a place on the front row. We looked at each other and shook our heads. No, not the front row, thanks. We'll sit a little bit further back. Cautionary Tales is written by me, Tim Harford, with Andrew Wright, Alice Fiennes and Ryan

Dilley. It's produced by Alice Fiennes and Marilyn Rust. The sound design and original music are the work of Pascal Wise. Additional sound design is by Carlos Sanjuan at Brain Audio. Ben Nadaph Haferi edited the scripts. The show features the voice talents of Melanie Gutridge, Stella Harford, Oliver Hembra, Sarah Jupp, Maseya Munro, Jamal Westman and Rufus Wright. The show also wouldn't have been possible without the work of Jacob Weisberg, Greta Cohn, Sarah Nix, Eric Sandler, Carrie Brody, Christina Sullivan, Keira Posey and Owen Miller. Cautionary Tales is a production of Pushkin Industries. It's recorded at Wardour Studios

in London by Tom Berry. If you like the show, please remember to share, rate and review. It really makes a difference to us. And if you want to hear the show ad free, sign up to Pushkin Plus on the show page on Apple Podcasts or at pushkin.fm slash plus. Thanks.