Permits
When visiting sites within the limits of the oases, the main considerations are your vehicle, supplies and driving skills. Things get more complicated, however, if you're aiming for a remote location or planning to cross the desert by an unusual route. For their own safety, motorists are required to stick to the main roads between the oases, and any major detours need official permission . The main issuing authority is Military Intelligence in Cairo (Army Group 26, Sharia Manshia el-Bakry, Heliopolis), whose remit covers the whole Western Desert. Permission to travel to Qara Oasis or the Qattara Depression may also be obtained from Military Intelligence in Mersa Matrouh. No permit is required to drive from Siwa to Bahariya.

Vehicles
The desert is a potentially lethal environment, so it's crucial to get the right vehicle. If you're not planning anything ambitious, a camper (mobile home) might be worth considering. The high price may be affordable when shared among four or five people; ask at Starco (1 Midan Talaat Harb, downtown Cairo; tel 574-6963). However, campers are too ponderous for crossing soft sand, salt flats or boulder-strewn pans, and their fuel consumption is prodigious (carry a full extra tank in reserve), ruling them out for serious ventures off-road.

Providing they're up to scratch, cars are better. Mechanical reliability, high ground clearance and four-wheel drive are absolutely vital; non-automatic gears, a water-cooled engine and an electrical fuel pump are strongly advised. Tyres should be in good condition and have inner tubes; always carry two spare wheels, a tyre pump and pressure gauge, levers and a jack. A fire extinguisher, vital spares and a full tool/repair kit are also essential. El-Tahawy Tops can usually provide cars that fit the bill.

Ideally, your vehicle should also have the following modifications : steel plates welded below the sump and fuel tank to prevent them being holed, fireproof lagging around the fuel lines where they pass the exhaust manifold, crossover seat belts, fabric-covered seats, an extra, false roof above the cab (painted gloss white for maximum cooling effect), and a mileometer for navigational calculations.

Equipment
You can never carry too much water (in metal or heavy-duty polythene jerry cans, securely fixed to brackets) or fuel - travelling off piste can reduce a car's normal mileage by half. Even staying within the limits of an oasis depression, it's vital to be able to orient yourself. A vehicle-mounted compass must be adjusted to the car's magnetic field, which will also distort readings on hand-held compasses if you stand too close (as do ferrous rocks in Bahariya Oasis).

Desert driving
Decide from the start whether you plan to travel on paved roads, unpaved tracks ( pistes), or through trackless open desert. It's safe to travel alone by road, as the police checkpoints at either end (and at intervals along major routes) will raise the alarm if you fail to arrive. Always travel in pairs of vehicles if you're going off-road (though locals often drive alone on familiar territory). Never set off - or keep going - during sandstorms; should you get caught in one, turn the car's rear end towards the wind, lest it sand-blast the front windscreen and headlights into opacity.

Driving at night is likewise taboo: potholes are vicious and it's easy to crash or get lost. The best times for driving are early morning and late afternoon, when there's less risk of overheating or misjudging the terrain. During the middle of the day, the details of the landscape are lost in the glare, making it harder to judge distances and scale . Both are distorted by the desert, where drivers often perceive near-vertical slopes as level ground, or discarded jerry cans as villages. These kind of optical illusions are commoner than mirages of shimmering "lakes".

If you are driving cross-country, stay alert for changes in the desert's surface , often indicated by a shift in colour or texture. Wheel ruts left by other vehicles can also yield clues: a sudden deepening and widening usually means softer sand (another sign of which is vegetation around the edges of dunes). Generally speaking, gravel plains provide a firm surface, while salt flats and dunes are the most unstable. Deflating one's tyres increases their traction on soft sand, but also their surface temperature and the car's fuel consumption, so keep a conservative speed.

Dunes
There's no substitute for experience of dunes , but a few points need making. Never crest a dune at high speed, in case the far side has collapsed, leaving a slipface. If you do go over, accelerate hard (which tends to lower the rear of the vehicle), charge down the slope and hope to butch it out. Braking or slewing sideways seems the natural reaction, but it's likely to somersault or roll the car over the edge.

When deflating tyres for better traction, do this just before you drive onto sand, and pump them up again before gaining firm ground. Shifting into a lower gear should likewise be done in advance. If stuck in soft sand, revving the engine will only dig you in deeper. Stop at once, change into low gear and try driving out slowly. If this fails, deflate the tyres as far as possible (or put traction mats, brushwood etc, beneath the rear wheels) and try again.

Emergencies
Getting stuck, breaking down or crashing in the desert can be fatal if you compound the misfortune by acting wrongly. Assuming you're driving solo, never leave your own vehicle unless you're within 5km of a plainly visible settlement or major highway. Otherwise, stay put, keep cool (literally) and try to attract attention. By day you can burn oil-soaked sand or bits of rubber to produce thick black smoke; at night, make a fire. A vehicle, smoke or fire are hard enough for search parties to locate; a person on their own is virtually impossible.

Other emergencies arise simply through drivers getting lost. The moment you suspect this, stop and try to get oriented using a compass, the sun, or the watch or stick method; take your time calculating how much water and fuel remain, then deciding on a course of action. The worst thing to do is simply drive on by instinct - it's a sure way of wandering even further in the wrong direction.

Although proper spares are obviously preferable, improvised materials can serve for vital repairs : nylon tights make a substitute fan belt and chewing gum can plug holes in fuel tanks or radiators.