The most important thing about desert survival is to avoid the need for it in the first place! Be aware your vehicle's capabilities and do not overload it, and know how to maintain and repair it. Carry adequate spares and tools. Be fit yourselves and get sufficient sleep. Start your journey with 25 per cent more fuel and water than you calculated would be needed to cover extra problems, such as bad terrain, leaking containers and extra time spent over repairs or sitting out a bad sandstorm.

Know accurately where your next supplies of fuel and water are. Carry plastic sheets to make desert stills and take space blankets with you. Pack more than one compass and know how to navigate properly. When using magnetic compasses, keep them well away from vehicles and cameras. Do not rely exclusively on electronic Global Positioning Systems (GPS) or the batteries that power them, and do not leave the piste unless you really do know what you are doing. Travel only during the local winter months. Know how correct your odometer is in relation to the wheels and tyres fitted to the vehicle. Make notes of distances, compass bearings and obvious landmarks as you go along so that you can retrace your route easily if you have to.

Observe correct check-in and out procedures with local authorities. If possible, travel in a convoy with other vehicles. When lost, do not continue. Stop, think and, if necessary, retrace your route.

Backup plans

If you are travelling in a large party, you should arrange a search and rescue plan before you start out. This would include the use and recognition of radio beacons or flares for aircraft search. Many countries do not allow you to use radio communications, but if you can use them, carry modern portable satellite communications systems.

Should the worst happen, remember that, for most people, an air search is highly unlikely and high-flying commercial passenger aircraft passing overhead are unlikely to notice you, whatever you do. A search, if it does come, will be along the piste or markers. Most often this will consist of other vehicles travelling through the area, whose drivers have been asked by the local authorities to look out for you because you have failed to check in at a pre-appointed time and place.

Local drivers will not understand or appreciate coloured flares, so your best signal for local outside help is fire. If you hear a vehicle at night, cardboard boxes or wood are quickly and easily lit, but during the day you need lots of thick black smoke. The best fuel for this is a tyre. Bury most of a tyre in the sand to control the speed at which it burns (keep it well away from and downwind of the vehicles and fuel) and start the exposed part burning with a rag soaked in either petrol or diesel fuel. As the exposed part of the tyre burns away, you can uncover more from the sand to keep it going, or cover all of it with sand if you wish to put out the fire. You should always avoid inhaling the sulphurous fumes. While the battery still carries a charge, headlights switched on and off at night can also be used to draw attention to your plight.

Should you be lucky enough to see low-flying aircraft overhead, it's worth remembering that the international ground/air code for a request to be picked up by such a plane is to stand up with your arms held aloft in an obvious 'V' shape.

A need to survive

Once you are in a 'need-to-survive' situation, the important things are morale and water. Concentrate on getting your vehicles moving again. This will keep you occupied and help to keep up morale. To minimise water loss, avoid manual work during the day and, instead, work at night or in the early morning. Build shade and stay under it as much as possible, keeping well covered with loose cotton clothing. 'Space blankets', with the reflective side facing out, make the coolest shade. Keep warm and out of the wind at night. In really hot climates, replacing lost potassium with Slow K can make a big difference to your general alertness.

Unless you are well off the piste with no chance of a search, you should stay with your vehicle. If someone must walk out, pick one or two of the strongest and most determined people to go. They must carry with them a compass and a GPS receiver, if available; a torch; salt; anti-diarrhoea medicine; loose, all-enveloping clothes; tough footwear; good sunglasses and as much water as they can sensibly carry. In soft sand, a jerrycan of water can easily be hauled along on a rope tied to the waist. On mixed ground, tie the jerrycan to a sand ladder, one end of which is padded and tied to the waist.

Those who walk out should follow the desert nomad pattern of walking in the evening until about 11pm, sleeping until 4 am, walking again until 10 am, then digging a shallow hollow in the sand and lying in it under a space blanket, reflective side out, until the sun has lost its heat. If it's a full moon they can walk all night. In this way, fit men would make 60-70 km on ten litres of water - less in soft sand.

Water

In a 'sit-it-out-and-survive' situation, with all manual labour kept to a minimum, food is unimportant and dehydration staves off hunger, but water is vital. The average consumption of water in a hot, dry climate should be eight litres per person per day. This can be lowered to four litres a day in a real emergency. Diarrhoea increases dehydration, so should be controlled by medicine where necessary. Salt intake should be kept up - in the worst scenario, licking your bare arms will replace some lost salt.

Water supply should be improved by making as many desert stills as possible. To make one, dig a hole about one-third of a metre deep and one metre in circumference, place a clean saucepan or billycan in the centre of the hole, and cover it with a two-metre-square plastic sheet weighted down at the edges with stones, jerrycans or tools. Put a stone or another heavy object in the centre to weigh it down directly over the billy. Overnight, water vapour from the sand will evaporate and then condense on the underside of the plastic sheet. In the morning, running a finger down from the edge of the sheet to the centre will cause the condensation to run down and drip into the pan. All urine should be conserved and put into shallow containers around the central billycan. The water so collected should be boiled or sterilised before drinking.

If you have antifreeze in your radiator, don't try to drink it as it is highly poisonous. Even if you have not put antifreeze in the radiator yourselves, there is still likely to be some left in it from previous use or from the factory at the time that the vehicle was first manufactured. Radiator water should be put into the desert still in the same way as the urine and the resulting condensate should be boiled or sterilised before drinking. Water from bad or brackish wells can be made drinkable in the same way. Note, however, that solar stills can take a lot of energy to create and will yield little water in return. Until the situation is really desperate, they are probably not worth considering as a viable means of collecting water.

The minimum amount of water per day required to maintain the body's water balance at rest in the shade is as follows: if the mean daily temperature is 35C, you will need 5.3 litres per 24 hours. If it is 30C, then 2.4 litres; if 25C you need 1.2 litres; and at temperatures of 20C and below, one litre will suffice. It must be stressed that this is the bare minimum necessary for survival. If such an intake is prolonged, there will be a gradual kidney malfunction and possibly urinary tract infection, with women more at risk than men.

The will to live is essential. Once you give up, you will be finished. If you find people in such a situation and do not have a doctor to handle them, feed them water to which rehydration salts have been added, a teaspoonful at a time, every few minutes for a couple of hours. If you do not have sachets of rehydration salts, you can make your own by adding one level teaspoon of salt and two tablespoons of sugar per litre of water. If the person is unconscious, the dissolved rehydration salts can be administered anally. It is essential to try to stabilise someone in this way before trying to take them on a long, tough drive to hospital.