This is the only road in South America where you must drive on the left. Vehicles climbing up from Coroico hug the mountain and have right of way. Those coming down from La Paz get to see the murderous drops at close range.

We ford a small river, raising the suspension and selecting Rock Crawl mode on the Terrain Response, before beginning the initial climb. The early part of the road is wide enough for two cars; heavy trucks have created a washboard effect on the dirt surface.

We round a corner to find an open area, almost like a quarry, although the only thing that you would dig out of here is mud. A bulldozer is parked, waiting for the next inevitable landslide. The ruts are deep, but the car momentarily locks its center differential to haul us through.

As we progress, the road is becoming steeper, narrower and busier with micros, pickups, tourist buses and huge trucks, all moving as fast as they can. According to the locals, just two weeks ago, two buses went over the side, resulting in the loss of 25 lives—rumor has it they were racing. Insane, obviously, but there are plenty of overtaking points, and slower traffic does have a tendency to move over if the horn is sounded with the right amount of enthusiasm.

It's just at the point when I'm starting to become a little too enthusiastic that I see the first of the red markers that marks the spot where someone has gone over the edge. And then we see the first of the crosses. At intervals along the 69-kilometre Death Road, there are more than a dozen memorials to those who have perished, including a plaque in Hebrew to commemorate the life of a 23-year-old Israeli tourist who lost control of her mountain bike and plummeted over the edge.

Mountain biking has become a huge business here, with more than 250 bikers heading downhill from La Paz every day in the peak season. Even today, with the road muddy and the weather alternating between heavy rain and shine, we see two groups of 10 riders, skittering down toward us.

They are soaked to the skin, and it's not just the rain. Around the corner a waterfall thunders down on the road. In a Range Rover Sport, with the wipers on, it's frightening enough, as the force of water dropping from 100 metres above hits the car. On a mountain bike, it must be terrifying.

As the ascent continues great banks of cloud fill the valley. This is the kind of view you would normally only get from an airplane. And when that cloud sweeps in across the road and the drizzle sets in, I'd certainly be happier if there were a parachute under my seat. It's a complete whiteout, and we slow to little more than a walking pace, eyes straining to seek out the edge, scanning for the frequent holes that suddenly reduce the road width by a third or more. But we persevere and climb out of the cloud.

The next section is the most dangerous of all. The road is narrow and twistier than ever. Prodigious use of the horn is required to let oncoming traffic know we're coming. I keep the car as tight into the side of the mountainside as possible. Even so, there are plenty of times when we have to brake to standstill or even reverse to let other vehicles past. We're supposed to have the right of way, and while the rule is generally well observed, sometimes it's easier for us to back up than for an overloaded articulated truck.

At six key danger spots, help is at hand. Volunteers act as human traffic lights, holding red or green signs up to shepherd the traffic.

52-year-old Timoteo has been flagging traffic every day on Death Road for the past 12 years. He has just a small timber-and-tarpaulin shelter to protect him from the elements, and he survives on handouts from grateful drivers. Why does he do this? Because in 1978 he lost his family over the edge and he wants to prevent it from happening to someone else.

Tales like this cement the road's reputation. The chances of surviving an accident, let alone being rescued, are very, very slim.

As a young medical student, our guide Hugo had been driving along the road with his father-in-law. Just a few hours earlier, a truck had gone over the side.

"We could hear the screams," says Hugo. "I wanted to try to help, but my father-in-law carried on driving. 'What would you do?' he asked me. 'You'd just kill yourself.' He was right, but I will never forget that."

We carry on, climbing toward La Paz, and within an hour are through the worst section, back on the right side of the road and heading once again for Unduavi on paved roads. It's a relief to be clear of Death Road. A few miles further, we have climbed to an alarming 4,700 metres. Several crosses and a statue of Christ sit on the high peaks. A number of small fires burn, the remnants of religious ceremonies to bless travelers on the hazardous trip to Coroico. Waiting nearby is Esteban Florres, an Aymaran sorcerer. He offers to bless us and our trip and, after a ritual involving coca leaves, alcohol, the burning of wax effigies of cars, and much chatter in a mixture of Aymaran and Spanish, he claims that from now on, we will have plenty of good luck. If only we'd met him a week ago.