Moab, Utah: An adrenalin-filled Hummer rock tour

"It's OK to scream," says Mike. Good to know because I'm about to start wailing like a teething toddler. Ahead of us is a steeply plunging wall of sandstone and we're going down it. Fast. I can't see what's at the bottom but I'm fairly sure it's certain death.

We career down the slippery rock, feet braced, knuckles gripped, stomachs lurching. While I shriek uncontrollably, Mike steers nonchalantly with one hand. Finally, we reach the valley floor and he expertly scrubs off speed and brings us to a stop. Everyone lets out a relief-fuelled sigh. No one died ... well, except my dignity.

Welcome to Hell's Revenge, a 10-kilometre, four-wheel-drive track in the Sand Flats Recreation Area just outside Moab, Utah. Most people use Moab as a base to explore the majestic national parks of Arches and Canyonlands (which are so frustratingly scenic you'll spend most of your time trying to take a photo that does them justice). However, Moab is also a magnet for adventure-lovers with outfitters offering hiking, rafting, biking, horse riding, skydiving, climbing and more.

By comparison, this Sunset Hummer Tour from the Moab Adventure Centre sounded relatively tame. Watch the sunset with a cold beverage from a rocky outcrop in the desert? I can do that.

We meet Mike at the company's headquarters in town and climb into the back of a customised bright red Hummer H1 – the commercial derivative of the 4WD Humvee utility vehicle favoured by the US military.

Ten minutes later we're at the entrance to Sand Flats, a 3600-hectare reserve of slick sandstone domes, yawning canyons and winding valleys of sand. Mike calls it a "giant adventure playground" because it's home to the world-renowned Slickrock mountain bike trail and more than 40 kilometres of 4WD tracks. Amazingly, anyone can turn up and have a go – all you need is a jeep, a $5 pass and nerves of steel.

"Are you ready for a two-hour rollercoaster?" asks Mike, as we creep up a steep, narrow fin of red rock flanked by vertiginous drops. Not really, I think to myself, anxiously tightening my seatbelt.

For the next hour we tackle terrain that would challenge a mountain goat. We skid down death-defying slopes, roar through sandy-floored chicanes and teeter precariously on rocky summits. Several times we only have three wheels on the ground. Throughout it all, Mike, who's been doing this for 17 years, radiates exactly the sort of relaxed mastery you want from someone who's about to drive up a lethally banked 50-degree slope. "Adrenalin is good for you," he says, grinning. "I'm actually 75."