By Tom Geoghegan
La Paz, Bolivia
Cycling the so-called world's most dangerous road is now one of the most popular activities for backpackers in Bolivia. Last month, shortly after what is thought to be the 18th biker death on its perilous hairpin bends, interest was undiminished. So what's the attraction?
It's a bike ride like no other.
No wonder it is known as the world's most dangerous road, or simply "death road".
On its upper reaches, the clouds hug the cliff edge, obscuring the abyss.
To the left, there is an unobstructed 600m drop off a cliff while on the right, a vertical rock-face.
And the surface, which is unpaved, resembles a rough, dirt track more than a road.
Some of the drops are hundreds of metres high
The scenery, if you dare take your eyes off the road, is breathtaking, with the lush rainforest of the Yungas stretching out before you. But the stone and wooden crosses that line the route are a sombre reminder that not everyone cycles the full 40 miles (64km) safely to its conclusion.
Hurtling at 30mph (48km/h) down its dusty track is now a sought-after thrill for about 25,000 backpackers a year.
It has become an extreme sport like bungee jumping and skydiving. The difference here is that there is no expert guide controlling your propulsion. You are on your own.
There are no official figures for the number of deaths but the first tour company to offer the ride, Gravity, says 18 backpackers have been killed since cyclists began tackling its hairpin bends 12 years ago. Other tour companies estimate the figure is slightly lower or higher than that.
The most recent victim was an Israeli backpacker, who died last month after going over the edge. No-one knows how the accident happened, but when cycling the route, the perils are obvious.
It is nearly all downhill, dropping 11,800ft, which means speed increases almost imperceptibly, and your hands are constantly applying the brakes. Then there is the uneven surface, the loose stones that make the ride even more hazardous.
Badge of honour
Although a new road opened in 2006, there are still a few lorries and cars vying for space with the hordes of thrill-seeking cyclists, on a road that is sometimes only a single lane wide.
The spots that claimed the lives of motorists and cyclists are marked
The highway from La Paz to Coroico was built by Paraguayan prisoners of war in the 1930s when the two countries were at war, and it earned its notoriety in 1995.
The Inter-American Development Bank was conducting a feasibility study for a new road and it estimated that there were between 200 and 300 deaths a year, so it bestowed on it the title of the "world's most dangerous road".
Those four words have now become a dubious badge of honour, a slogan seen on backpacker T-shirts and a phrase overheard amid the bravado of youth hostel bars.
"If you go to London, you have to see London Bridge and if you go to Sydney you have to see the Opera House," says Andrew Jagoo, 26, from Melbourne, recovering his breath after the ride.
The number of lives lost used to total more than 200 a year
"And if you go to Bolivia, you must do the most dangerous road. There's an element of risk but you can say afterwards that you've done it."
The man who started the phenomenon in 1998, 39-year-old New Zealander Alistair Matthew, says good instruction and sensible behaviour can overcome the dangers.
"It is our belief that the vast majority of the risk can be mitigated by providing people with great bikes and equipment, lots of instruction, and lots of warnings about the potential for accidents.
"However, this also means constantly monitoring groups to provide extra warnings to over-excited people and more coaching to less experienced riders."
He came up with the idea while trying lots of new rides on his mountain bike in the region near La Paz.
"The first ride down the world's most dangerous road was spectacular. I went with a British lad, ex-SAS, both of us on horrible old-school bikes with no suspension and cantilever brakes.
"We finished the ride with big grins and 'claw-hands' from holding on to the brakes."
His company, Gravity, was the first to offer tourists the chance to cycle the road, initially five people at a time.
It is now one of up to 20 companies promising backpackers the thrilling whiff of danger. Gravity uses a trained guide to cycle at the front and one at the back, plus sometimes one in the middle. And a minibus carrying spare bikes and rescue equipment follows behind.
During the rainy season, from December to March, he says Gravity discourages people with little or no experience from taking part.
Although only one rider with Gravity has had a fatal accident - a man in his 50s about two years ago - there are plenty of cuts and bruises. Roughly every fortnight, someone requires hospital treatment for an injury.
DOs and DON'Ts
Don't try to race others
Don't do it with a hangover
Listen to the instructors
Warn people when you overtake them
Stop and dismount to take photos
Only experienced riders should do it in the rainy season
"Simply put, it's all about 'bragging rights'," says Mr Matthew. "Everyone wants to return from their holidays and travels with good stories to tell their mates at work or at the pub, or to post on Facebook.
"The road is simply unparalleled in that regard and the accidents on the road add to that story."
The news of the Israeli woman's death was the talk of the youth hostels in La Paz in the days afterwards, and some backpackers said it had put them off doing it.
One Israeli in his early 20s said you would have to be "crazy" and he said he had promised his parents that under no circumstances would he undertake this cycle ride.
Cyclists are kitted out with helmets, gloves and hi-vis jackets
Even those who took to the saddle a week after the tragedy said the news added to their anxiety.
"I was really scared and I was even crying beforehand," says Marte Solberg, 22, from Norway, after completing the ride.
"A lot of people had said it is so much fun, but I was scared of falling over and dying, like the Israeli girl. I was worried about my own judgement because I have no experience of mountain biking. One mistake and you are dead.
"I asked myself a thousand times 'Why am I doing this?' The answer is that firstly, everyone is doing it. If you come to Bolivia, you have to cycle down the most dangerous road in the world. And secondly, it's a personal challenge."
The clouds on the higher stretches obscure the drop
Catherine Pearson, 28, from Manchester, on a six-month trip with her boyfriend, believes you could simply be unlucky.
"If a truck comes along and you go over a stone the wrong way, you don't know what could happen. Sometimes while I was cycling, I was thinking 'I'm going too fast, I need to brake' and then I braked and I thought 'I'm braking too hard and might tip over.'
"It's a personal challenge and you are scared but it's a balance between the two. You have to beat your fear."
But the news of what happened a week before did change the tone of the day, says Ms Pearson.
"Hearing about the death had an impact on us. For a start, it made me pay extra attention. And you would feel guilty if you started bragging about surviving."