As the Unduavi-Yolosa Highway in Bolivia winds down 12,000ft (3.6km) over 40 miles, its sheer drops and sudden bends present an irresistible challenge for thrill-seeking mountain bikers.

But the wooden crosses and the bouquets of wilting flowers on each side are testimony to a stretch of dirt track known as El Camino de la Muerte, the Road of Death.

A young British cyclist and eight others have become the latest to lose their lives on the road officially named as the most dangerous in the world.

Tom Austin, 22, from West London, was cycling with two friends when they were involved in an accident involving a Toyota Land Cruiser on Thursday. The vehicle rolled 300ft down a rocky embankment, killing eight people inside and injuring five others.

Mr Austin had been cycling with Daniel Roberts, 23, and James Marshall, 22, who were being treated in hospital for their injuries last night.

Mr Marshall, said: “I heard a loud noise behind me and the next thing I know is something has come through the back of me.

“I’ve kind of come to on the side of the road with a pile of bikes on top of me. Apparently what happened was a Land Cruiser was passing us round the outside and its tyre blew and it swerved through the row of cyclists.”

Victor Fabia, one of the guides on the tour organised by Downhill Madness, said 20 people were taking part in the ride, about 12 of them from Britain.

“We had gone through all the safety checks and had been riding for about five minutes when a Land Cruiser came up very fast on the left-hand side,” he said.

“It hit three of the British men and then went over the side. There was nothing we could do, it happened very quickly.”

Louise Taylor, vice-consul at the British Embassy in La Paz, said that the riders were not taking part in a race, as far as she was aware.

The “Road of Death” has become one of most popular challenges for young people on gap-year or post-university trips.

Barely a dirt track, at points the road is less than 10ft across. During the rainy seasons it can become a shifting, slippery mass of mud. Blind bends and rolling mist conceal oncoming vehicles, many of which are 30 or more years old.

Lieutenant-Colonel Agusto Angulo, head of the La Paz transit police accident division, said that the accident happened minutes after the cyclists began their tour on a paved section near a 15,400ft Andean pass.

Mercedes Solis, a lawyer for Downhill Madness, insisted that the cyclists were riding on the hard shoulder.

The highway east from La Paz, the world’s highest capital city, winds dramatically down the face of the Andes. The narrow, largely dirt track earned its macabre nickname for the frequency with which Bolivian buses would plunge off its 3,300ft cliffs, killing hundreds of people a year until a new paved highway opened in 2007.

The old route’s stunning vistas and hairpin turns still draw an estimated 25,000 mountain bikers from around the world. At least 13 cyclists have died on the road in the past ten years. The Inter-American Development Bank designated it the most dangerous road in the world, based on deaths per mile.

On Monday Kenneth Mitchell, 56, of Fullerton, California, died when he tumbled from his bicycle and fell over a 200ft cliff along the road.

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