The wall of water makes it impossible to see ahead, but the road surely must continue on the other side. For a few seconds I'll be driving completely blind, knowing that if I'm just a few feet off course, I'll plummet to a certain death in the jungle thousands of feet below.

So I breathe in, flick the wiper switch and gently press down on the Range Rover Sport's accelerator, feeling the tire tracks resonate through the rim of the steering wheel.

The noise is deafening as torrents of water slam into the windscreen and roof. The wipers are on full speed, but I still can't see the road. I tighten my grip on the wheel, nudge the throttle again and emerge breathing a huge sigh of relief, having survived one of the many hazards of the World's Most Dangerous Road.

This was never going to be a safe trip to Bolivia, but that was the point. We are on El Camino de la Muerte—Death Road—commonly believed to be the most dangerous road in the world. And for good reason. In a relentless series of switchbacks, it climbs over 1,000 metres before plummeting another 3,200 metres in less than 70 kilometres, winding its way across treacherously steep Andean mountains from La Paz (at 3,600 metres, the world's highest capital city), through waterfalls, past thick rainforest and down to the lush rolling farmland that surrounds Coroico.

Admittedly, it's probably not what the Land Rover engineers had in mind when they decided to give the Range Rover Sport some on-road bias, but this is still a 4x4 with Land Rover DNA and, well, it had all seemed like such a good idea when we started out.

Rewind two days. I arrive in La Paz and with my chest heaving and brain pounding from the lack of oxygen, hear some statistics that make me feel even more lightheaded. "In eight years, I have attended maybe 30 accidents, involving about 250 people," Captain Henard Romero of Police Rescue tells me. "Of those, we have only managed to rescue around 100. The reason that the death toll is so high is that the trucks and buses that travel the road are overloaded with people. In 2002, we had four buses that went over the edge." Bespectacled and in his mid-30s, Romero has the look of a young geography teacher, not a seasoned road cop used to dealing with disaster scenes. He speaks without emotion. Except when I use the expression "Death Road." "I do not like that term. It is just a road," he says firmly.

It's much more than just a road to some, though, as I was to find out when we set off in the Range Rover Sport at the beginning of our journey. Death Road is the main link between the capital and the Yungas, the lush high-altitude rainforest that provides the fruit and the tourism, not to mention the coca leaves, that keep this region alive.

It's the coca that's the political issue of the day and the reason why men, women and children have been blocking the road at Unduavi (about 40 km from La Paz, just at the start of Death Road). These people are cocaleros—coca farmers—and up to 1,500 of them have been camped out in the wintery conditions that blight the area at this time of year. They've had no sanitation, little food (although no shortage of alcohol or coca leaves) and plenty of rain. They're demanding the destruction of a nearby police garrison and they want the government to improve the roads and allow more commercialization of coca.

It is not illegal to grow coca in Bolivia. The leaves are used medicinally, chewed recreationally and brewed to make tea. Coca does, of course, have another more profitable, and illegal, by-product. And with the United States' war on drugs being fought all over South America, the cocaleros are fighting for their survival.

"We don't care how long it takes," one of their spokesmen tells me via our guide, Dr. Hugo Berrios, when we climb out of the car. "We will stay if it takes until the next carnival."

As he talks, a crowd gathers. I try hard to concentrate, to hold my camera still, to appear confident—the seasoned reporter. And it actually works—the camera gives me added credibility. At the end of the interview, I flash an old BBC business card and a whisper spreads through the throng. The cocaleros part to let me go; some even smile. It's then that I notice the machetes dangling from many a waistband.

Berrios offers two choices: Try to bribe our way past the blockade and drive Death Road from south to north as planned, or embark on a lengthy detour around to Coroico, and drive Death Road back to La Paz, starting at its northern end.

Suddenly there's a huge explosion behind us and the air becomes thick with acrid black smoke. Instinctively, I put my foot down on the accelerator. That seasoned reporter from two minutes ago is now desperate to get on the first business-class flight out of here.