Lionel Wood did not even flinch. He just wheeled his mammoth maroon lorry and its 80-ton load off the Tarmac and down on to the frozen lake. A flick of a switch, and the passenger window wound down. 'Hear that?' he said, smiling wryly. Outside, the temperature was minus 35C and the air was full of pops and bangs, as if a child were firing a cap gun - except that these bangs were potentially deadly.

As the last of the lorry's 42 wheels rolled on to the lake, the glistening surface cracked. Hundreds of tiny fissures, 20ft long, shot out under the tyres. The ice looked like crazy paving as it took the immense weight of the 100ft-long mining dump truck. 'The cracking is a good sign,' Lionel said. 'It means the ice is flexible.'

Only three feet of frozen water was keeping us from plunging to the bottom of the lake. 'It's OK,' Lionel said, unconvincingly. 'The chances of going through are fairly slim.' He closed the window and turned up the stereo. At least now the pops and bangs were drowned out. 'If you thought of it as just ice and water, you'd lose your nerve,' he said.

With a girlfriend and a two-year-old daughter at home in Edmonton, Alberta, Lionel, 28, had needed some enticing to leave for three months and risk his life on one of the highest paid and most challenging driving jobs in the world.

From January to March, the harshest period of the Canadian winter, 57 lorry drivers working for Robinson Trucking in Yellowknife, the capital of the Northwest Territories, spend seven days a week driving heavy and dangerous loads across hundreds of miles of ice roads to gold mines such as the one at Lupin, 405 miles north-east of Yellowknife and only 50 miles south of the Arctic Circle.

There are no permanent roads to many of the mines. For most of the year they are cut off by hundreds of lakes. Only when these freeze over can Robinson's plough ice roads across the territory. The task is a precarious one. In late January, when the lake ice is barely 18in thick, pathfinder teams set off in lightweight, balloon-tyred snowploughs to forge a way through many feet of snow. When the ice is exposed to the bitterly cold air, it soon thickens to the required 3ft.

Forty-four yards wide, in some places as smooth as a pool table and in others as rutted as a farm track, the road from Yellowknife to the Lupin mine weaves across lakes and over 'portages', across the small islands that in winter become refreshingly solid links in the ice.

It takes two days to drive the Lupin road. The lorries crawl across the barren snowscape like huge snails carrying bulky equipment and food to supply the mine for the nine months of the year when the only access is by air.

The annual operation is a logistical marvel. Every winter, Robinson's lorries make 860 return journeys to Lupin, equivalent to more than 25 times around the world. In three months, they bring in 7 million kilograms (16 million pounds) of equipment and explosives, and 22 million litres (5 million gallons) of fuel. Life on the ice roads is a lonely one. Hour after hour, the groan of the engine and the background of country and western music are interrupted only by the crackling of a two-way radio, the drivers' lifeline. The talk, sprinkled with jokes and liberal language, is mainly of the road and their rigs.

The temperature outside dropped to minus 46C as we left the protection of the pine trees. Inside the cab it was toasting, but frost edged the inside of the windscreen. Lionel's cab was palatial, with a deep pile of blankets and a sleeping bag filling the sleeping compartment: a home from home, which the drivers often prefer to sleeping in a camp.

The sight of the first of the two mining camps that have been converted to comfortable truckstops was a welcome one. Nine hours on the road, physically draining and mentally tormenting, had left the drivers in need of sustenance.

Our radio call to Carol in the kitchen at Lockhart camp paid off: a huge steak awaited each driver. In silence, they wolfed down the platesful; Carol and Stella, the camp's two full-time cooks, are used to the food being demolished with little ceremony. The truckers do not always have a choice of where they sleep; ice and snow storms can whip up across the lake without warning and strand them for up to a week. 'Sometimes you can't see 10 feet in front of you,' Lionel said. Another driver, Bob Baert, who once spent two days stuck on a lake as he waited for a storm to pass, said: 'Sitting them out is not very nice, but I just listened to the stereo and joked around on the citizens' band radio with the other drivers.'

In 30 years, Robinson's has not lost anyone driving on the ice roads, although one man died in 1970 after falling through some thin ice he was standing on. And Angus Charlo, one of Robinson's drivers, had a lucky escape in 1983, when his truck plunged through the ice, trailer first. 'It went down and stood up on its end, with water up to the dashboard,' he recounted. 'I had only two or three inches of air to breathe in.' He tried three times to escape from the cab through a side window, but was thwarted by the framework of the truck's huge rearview mirrors. 'Eventually I got out and jumped for some solid ice,' he said.

After the accident, he stopped ice-driving for six years, but returned two years ago, enticed no doubt by the money that draws most of these men to the job. Several drivers earn more than Cdollars 20,000 ( pounds 10,000) in the three months. That includes danger money, but because they are paid by the run, not by the time they take, they lose money if they are delayed.

While the road was open, Lionel did not want to hang around at Lockhart a moment longer than necessary. The run was probably his last of the season, and the memories of his daughter, Chelsea, whose picture was hanging in the cab, were proving stronger than the urge to make a few extra dollars on another trip to Lupin.

Thoughts of home disturbed Lionel's concentration. Then the conversation changed and he relaxed again. The ice began to pop and crack as the 80-ton monster crawled on to the aptly named Pensive Lake. 'You know what,' he said. 'I don't swim too good.'

(Photograph omitted)