Driving tests

How do you drive on mountain roads?

Heading away snowboarding this winter? You’ll almost certainly need to drive on mountain roads, as you will if you are crossing the ranges for work or family visits. Roads on mountains vary from well-maintained state highways down to rough tracks. Whether you are thinking of taking your first trip in the mountains in your vehicle, or this is your 40th year heading off skiing, you’ll learn something in this guide.

This guide supports the course Driving in Difficult Conditions which is the ultimate bad weather driving online course, teaching you about driving in snow, ice, floods, fog, torrential rain, and more.

Ruapehu mountain road in summer

How does the weather change?

Increasing altitude (height above sea level) means decreasing temperatures. The higher you go, the more easily the weather can flip like a switch: sunny one minute, massive blizzard the next. Roads can become impassable quickly. Fog can form in a matter of half an hour. Winds can pick up and make it treacherous for high-sided vehicles.

At night, the temperature drops quickly, and rain can turn to snow, with wet roads forming icy patches.

Snowy roads have to be cleared for them to remain passable in heavy snow

The terrain affects how water runs off the land and how the wind is diverted across the road.

Water and rocks

Waterfalls

Roads up mountains are frequently cut into banks. They’ll cross natural watercourses down the mountain. Often, they are piped under the road, but in some cases, there’s a small waterfall next to the road which might only be present when it rains. As night falls, these can freeze, forming dangerous icy areas.

Where the water is flowing deeply across the road, it can cause aquaplaning

Landslips

In torrential rain, waterfalls can spill over the road. Water also loosens rock and soil, causing landslips to slump over the road, and individual rocks to roll down the hill. These are common where freeze/thaw cycles crack rocks and loosen soil. Rockfall can happen over an extended time as more and more rocks come down.

When the ground is saturated enough, a layer of water can form above the bedrock that the soil sits on. The soil starts to ‘creep’ down the slope then, under the right conditions, a large section will shear away from its surroundings and slide down the hill until it reaches an obstacle. Landslips tend to happen just the once if they are deep enough. This is because vegetation is holding the soil together, and the body of soil slides off the supporting rock, so there’s no more soil to come.

Landslips are difficult to see at night, and it’s not unusual for a driver to come around a corner and be faced with a landslip that they don’t see until the last minute.

Occasionally, drivers have been swept off the road in a landslip if it has hit their vehicle while they are driving.

Washouts

A washout is where water erodes or weakens the soil under the edge of a road and it eventually falls away, leaving the road with no support.

Metal (unpaved) roads

Unpaved gravel or dirt roads in mountainous areas get potholes and corrugations quickly. Potholes can damage your suspension, while corrugations are extremely uncomfortable to drive on.

The gravel itself mostly has reasonable grip within the main tyre tracks, but if you venture onto the thicker gravel, or if all the gravel has worn away, then traction is compromised and you can find yourself with no steering or braking.

Sun strike

As you are facing up the mountain, you are angled towards the sun more so then when driving on flat terrain. Driving in winter also leads to longer periods of sun strike because the sun goes down at an angle. Take sunglasses and ensure your seat height is set so that you can use the visor.

Distractions

The scenery is what many people go to the mountains for. Don’t be distracted looking out the side windows as you’re driving. If you want to take in the view, get out and stop.

Don’t get distracted by the view. If you want to take a look, stop somewhere safe

Check for road signs

As the roads are narrower, there will often be priority signs where vehicles need to wait. In most cases, the drivers driving downhill give way to drivers driving uphill, although this doesn’t always apply on bridges.

Road signs will let you know when particularly gnarly corners are coming up, when there’s a risk of rock fall or landslips, or where the road might be slippery.

Braking distances

Braking distances downhill are longer than uphill because gravity is pull the vehicle down the hill at the same time. Conversely, uphill braking is shorter.

Many heavy vehicle owners have found they run out of braking power when half way down the hill, leading to total brake failure and a crash.

To minimise the work the brakes have to do, get your speed right before you start going downhill. Otherwise you can get brake fade, especially if you are towing a trailer or your vehicle is heavily laden.

When driving, look for technology that holds your vehicle back. These include moving the gearbox to a lower gear to be easier on the brakes. If you’re aiming for 40kmh downhill, brake to 35kmh, change down, then let the truck build up speed itself. Then bring the speed down; riding the brakes can create a lot of heat in the discs, whereas keeping your vehicle slow and in a low gear gives the brakes time to cool down.

Trucks have retarders and light vehicle operators can use the gears for engine braking.

Fuel planning

Fuel stations on mountains are pretty difficult to find. Ensure you have enough before you set off.

Stay with the vehicle

Never leave your vehicle unless you absolutely need help. It can be deceptively difficult to find someone in drifting snow. Floods can wash people and vehicles away. If you have to leave, leave a note giving instructions about where you have gone.

Emergency equipment and supplies

When going up, it’s ideal to take spare food, water and blankets. Be prepared that you might be stranded for up to a couple of days. If you’re on your own, it might be difficult for rescuers to see you.

Difficult road conditions

Exposed bridges are problematic for trucks, buses and other high-sided vehicles as strong winds funneling down a valley can push them across the road or, in the worst case scenario, blow them over.

Narrow mountain roads have less runoff area to act as a buffer, and if you meet wide or long vehicles, you may need to pull over.

Wildlife

Deer and pigs are common in some mountain areas. Also, be cautious for endangered birds, like kea.

Emergency equipment

If you’re driving in a mountainous area in winter, you’ll need a good emergency kit because it’s easy to die of hypothermia if you run into problems. At minimum, you’ll need snow chains and a shovel, blankets for warmth, spare food and water, and a torch. If you want to be even more prepared, ensure you have deicer and a scraper, flares and a personal locator beacon (cellphone coverage in mountainous areas can be patchy).

Part of being prepared also means keeping your vehicle relatively full of fuel in case you do get stranded. There are large stretches of mountain roads with nowhere to refuel. Carry a can of fuel if you need to.

Finally, paper maps can win out over GPS maps if there’s no coverage.

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Darren is a member of the Institute of Advanced Motorists and the NZ Motoring Writers' Guild

Posted in Advice
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