Australians measure distance differently, and this highway is why. The run from Perth to Port Hedland, taking in the Brand Highway that feeds into the route's southern end at Geraldton, stretches more than 1,700 kilometres - and even that is dwarfed by the nearly 2,700 kilometres between Adelaide and Perth. The coastal highway itself, Geraldton to Port Hedland, is the 1,300-kilometre core of it. North of Geraldton you pass within reach of some of the largest iron ore deposits on Earth and over some of the planet's oldest exposed rock. The country does not announce these wonders. It simply rolls on, red and flat and enormous, and lets the odometer tell the story.

Between Geraldton and Carnarvon the road crosses roughly 400 kilometres without a single town - only roadhouses, and they do not hand out water for free. Carnarvon, the one real settlement on the whole northern run, arrives like an oasis: bananas and subtropical fruit grow in its plantations, fed by the Gascoyne River, even as it ranks among the windiest places in Western Australia. Beyond it the land flattens further. Bridges leap dry creek beds you would never notice but for the lines of eucalypts that trace the watercourses, standing tall above the spinifex and mulga. Most of the year those riverbeds are bone dry. Between November and April, a passing cyclone can fill them from nothing to ten metres deep in less than a day.

The highway is a spine, and its side roads lead to some of Western Australia's finest country. Near the Minilya Roadhouse, a turnoff runs out to North West Cape - to Exmouth, Coral Bay, and the Cape Range National Park that fringes Ningaloo Reef. The Overlander Roadhouse marks the start of World Heritage Drive to Shark Bay and the famous dolphins of Monkey Mia. Inland branches climb to the iron ore towns of Tom Price and Paraburdoo, and past Wittenoom, the asbestos ghost town the maps would rather forget. The road itself stays modest; what it connects is extraordinary.

The highway's northern end belongs to industry on a colossal scale. Karratha and its sister town Dampier anchor the North West Shelf gas project and the region's second-busiest iron ore port. Roebourne opens the way to Wickham, to Point Samson, and to the ghost town of Cossack. The road finally meets the Great Northern Highway near Port Hedland - the number-one iron ore port in the region and, with around 15,000 residents, one of the larger towns in the state's northwest. From a dusty start at Geraldton, the highway ends where the trains a couple of kilometres long roll their red cargo onto ships bound for the world.

This is a road that punishes inattention. Its long, hypnotic straights have lulled drivers to sleep at the wheel, and fatigue is named again and again as the cause of serious crashes out here. Road trains - the multi-trailer freight haulers that own this highway - need kilometres of clear straight road to overtake safely, and overtaking one demands the same. At dawn and dusk, wildlife drifts to the verges. The roadhouses are not just fuel stops but survival points: coffee, a stretch, a chance to shake off the trance of the empty miles before pressing on into the next long stage.