What do I do if the road is flooded?

Every year in Australia people die in flood waters after driving through without consideration of the danger.

It's been well established that once the water rises above the door sills, escape from a vehicle becomes increasingly difficult. Often, the only means of escape once the water is above the window line is to smash a window with a hammer or some other heavy object handily lying around in the car for just such an eventuality.

Even heavy-duty four-wheel drives can be death traps if the water level is so high that the vehicle gains buoyancy and the tyres lose touch with the road surface. Who hasn't seen a news story on television featuring a big off-roader washed up on the shore of a river in flood – and the occupants drowned?

Of the 73 Australians who drowned between 1997 and 2008, according to the Royal Lifesaving Society of Australia, 48.5 per cent were related to motor vehicle use. A peer-reviewed article by the Australian Institute for Disaster Resilience has recommended that drivers of passenger cars avoid entering flood waters more than 30cm deep and four-wheel drive operators should steer clear of flood waters 50cm deep.

Fording a flooded stretch of water in the dark, with rain pouring down and the wind blowing a gale is one of the most dangerous things anyone can do in a motor vehicle.

As soon as you spot water over the road, turn back. If the vehicle has sufficient ground clearance, visibility is adequate and other vehicles are wading through without trouble you might give it a go, but it's not recommended.

The road may have crumbled at the edges below the water line and if the bed underpinning the road has subsided, the whole car could sink and drown the engine, or there may obstacles like trees or rocks submerged under the water and ready to snag you and your vehicle.

At the very least you could be up for a bill worth thousands to a mechanic repairing your engine. Maybe there'll be damage done to the electrical system as well.

Your insurer may not be happy either, counting the cost of replacing a vehicle written off due to flood damage. And you can bet your premium will cost you more next year.

Staying out of danger may not be as simple as it seems, however.

In urban areas, drivers are occasionally caught out following a line of traffic into a flooded section of road because they haven't looked far enough ahead – and while everyone else is driving an SUV or one-tonne ute, the driver in the small sports car is the person who will inevitably run into strife. Don't be a sheep.

If you expect to encounter flooding, because the heavens opened up the night before, leave plenty of braking distance and look well ahead. Always look for an escape route too. This is especially important in remote regions where alternatives are few and far between.

If the road – a dual-carriageway arterial for instance – is partly submerged, don't pull over. The camber of the road will lead you into deeper water. If the road in the centre is not completely flooded, stay in the right lane and maintain a speed that's right for the conditions. You don't want to be building a bow wave in an MX-5.

Flooding is at its most dangerous around fords and causeways. This is typically where the road dips on a floodplain and can channel deep, fast-moving currents during and after a deluge.

If you're confronted by a crossing in this sort of state, stop before the crossing, take off your shoes and socks, roll up the trouser legs and walk the course to check its depth and how firm the surface is under the water. If the water is above the knee of an adult of average height, don't even attempt to drive across – not even if you're in a four-wheel drive. If the water is half-way up your shin, think seriously about entering the flood water in a passenger car (i.e. not an SUV).

Be advised also, just because you can wade through flood waters along the centre line of the road, that doesn't mean it's safe to drive a vehicle through if the road has subsided at the edges or even half a metre left of the centre line.

In the event that you've decided to give it a crack anyway – and again, that's not recommended – make sure you pump the brakes on the other side and ensure they're working properly before you proceed any further.

People often decide to enter flood waters because they're time poor. Particularly out in the country, a detour could add hours to your trip.

But short of an emergency, practically nothing warrants taking the chance of drowning the car and putting yourself and passengers at risk when there's a better alternative.

So, the final word? At the first sign of flood waters... turn back.