Travelling overland in your own vehicle gives you the independence and freedom to go where you like, in a way that no other form of travel can ever hope to match. It also provides you with a familiar bolt-hole that can take you away from the milling crowds and the alienation one tends to feel in a different culture. The vehicle may seem expensive to start with, and can involve you in mountains of bureaucratic paperwork, but considering the cost of transport and accommodation, it becomes a realistic way to travel, particularly when you can escape the bedbugs and dirt that often accompany cheaper accommodation.

Which vehicle?

The choice of vehicle will be a compromise between what can be afforded, what can best handle the terrain to be encountered, and whether spares, fuel, food and water have to be carried or are readily available en route.

For a protracted transcontinental or round-the-world journey, you need to consider what sacrifices have to be made to balance the benefits of the more cramped vehicles, including the length of time you expect to be on the road and the degree of home comforts you will want along the way.

Where tracks are narrow, overhung and subject to landslides, as in outlying mountainous regions such as the Karakoram, the only usable vehicles are the smallest, lightweight four-wheel drives, for instance, the soft-topped short- wheelbase Land Rovers or Land Cruisers and the smaller Jeeps. These vehicles also give the best performance when traversing soft sand and steep dunes, but their small payload and fuel-carrying capacity restrict them to short journeys.

If you do not plan to encounter soft sand, mud or snow and your payload consists mainly of people, who, when necessary, can get out and push, you really only need a two-wheel drive vehicle, provided that it has enough strength and ground clearance.

Avoid large American-style conversions. They have lots of room and such home comforts as showers, toilets, microwave ovens and storage space; but their large size, heavy fuel consumption, high weight, low ground clearance, poor traction and terrible approach and departure angles make them unsuitable for any journey off the asphalt road. They also often have engines with electronic control systems, which are not repairable if they go wrong in the Third World.

If cost presents no problem and all spares are to be carried, the ideal vehicle would be an all-wheel drive with a payload of one tonne, evenly distributed between all wheels. Look for a short wheelbase, forward control, high ground clearance, large wheels and tyres, good power-to-weight ratio and reasonable fuel consumption. The vehicles best fitting this specification are the Mercedes Unimog, the Pinzgauer and the Land Rover Military 101 'one tonne'. These are specialist vehicles designed for best cross-country performance and are often soft topped to keep the centre of gravity low. However, the costs involved in buying, running and shipping such vehicles would deter all but the very wealthy.

Considering price, availability of spares and working life, the most commonly used vehicles are the long-wheelbase Land Rovers, the smaller Mercedes Unimogs and the Bedford M-type trucks. The VW Kombi and the smaller Mercedes panel vans are the most popular two-wheel drive vehicles. These are big enough to live in and carry food, water, spares, cooking stoves, beds, clothes, extra fuel and sand ladders. They also remain economical to run, small enough to negotiate narrow bush tracks and light enough to make digging out less frequent and easier.

These vehicles will carry two people in comfort, more if camping or using other accommodation overnight.

A high-roofed vehicle is convenient to stand up in and provides extra storage, but is more expensive on ferries. It also offers increased wind resistance, thus pushing up fuel consumption and making the engine work harder and run hotter. This shortens engine life and increases the risk of mechanical failure.

Trucks

Where heavier payloads are envisaged, such as in Africa, where you will often have to carry large quantities of fuel, the most popular four-wheel drive vehicles are the Bedford M-type trucks and Mercedes Unimogs. Bedford trucks are cheap, simple and, in some ways, crude. They have good cross-country performance when handled sensibly and slowly, but are too heavy in soft sand. They go wrong and bits fall off, but repairs can usually be improvised, and used spares are readily available.

Bedford M-type trucks are best bought ex- UK military, as are their spare parts.

Ex-NATO Mercedes Unimogs are near to perfect for heavy overland or expedition work. Their cross-country performance is exceptional, and their portal axles give them extra ground clearance, though this also makes them easier to turn over. It is almost impossible to get them stuck in sand, though they will stick in mud. They usually have relatively small petrol engines, so you need to use the gearbox well, but fuel consumption is good. The standard six-speed, one- range gearbox can be converted to a four-speed, two-range gearbox, which is useful in sand. Four-wheel drive can be engaged at any speed without declutching. Differential locks are standard. The chassis is arranged to give good weight distribution over all four wheels at almost any angle, but this causes a bad ride on corrugations.

Mechanically, the Unimog is over-complicated. It doesn't go wrong often, but when it does it is difficult to work on and often requires special tools. Later models have the clutch set to one side of the transmission, instead of in line with it, making it much easier to change. Unimogs are best bought from NATO forces in Germany. Spares must be carried with you. Diesel Unimogs are usually ex-agricultural or building contractor, and are therefore less well maintained than military vehicles and may have rust problems.

Land Rovers

Despite some weaknesses, Land Rovers are the most durable four-wheel drive small vehicles on the market. Their spartan comforts are also their main attributes! Most of their recent challengers are too softly sprung and have too many car-type comforts to be reliable in difficult cross-country terrain. Spare parts are readily available worldwide and they are easy to work on with most parts bolted on. The older Series III leaf-sprung models, are more durable than the newer 'Defender' models, and leaf springs are easier to get repaired in the Third World. The aluminium alloy body does not rust, so bent body panels can be hammered back into rough shape and then forgotten. You don't have to be Hercules to change a wheel.

The short-wheelbase Land Rover is usually avoided because of its small load- carrying capacity; but in off-road use, particularly on sand dunes, it has a distinct advantage over the long-wheelbase models. Hard-top models are best for protection against thieves and safer when rolled, unless you have had a roll cage fitted.

When considering long-wheelbase models, it is best to avoid the six-cylinder petrol engine models. All cost more to buy, give more than the normal amount of trouble, are harder to find spares for and recoup less on resale.

The six-cylinder petrol engine uses more fuel and more engine oil than the four- cylinder petrol engine and the carburettor does not like dust or dirty fuel, which means that it often requires stripping and cleaning twice a day in very dusty areas. The electrical fuel pump gives trouble. The forward control turns over easily and, as with the Series IIa Land Rovers, rear half-shafts break if the driver is at all heavy footed.

The four-cylinder models are underpowered, but the increased power of the six cylinder does not compensate for its disadvantages.

The 109" V8 Land Rover has permanent four-wheel drive, with a lockable central differential. It is an excellent vehicle, but very costly on fuel.

The Land Rover 90 and 110, now renamed 'Defender', are designed for speed, economy and comfort on the newer, improved roads in Africa and Asia. Built on a strengthened Range Rover-type chassis and suspension, with permanent four- wheel drive and centre differential lock, stronger gearbox, disc brakes on the front and better doors all round, the vehicle is a vast improvement on earlier models. It is ideal for lightweight safari or personnel carrier use, but for heavy expeditions the coil springs should be upgraded or fitted with airbag-type helper springs.

In European Union countries, outside of the UK, 12-seat Land Rovers should be fitted with a tachometer and come under bus regulations.

Range Rovers and Land Rover Discoverys are not spacious enough for long journeys, nor do they have the load-carrying capacity.

Any hard-top or station wagon Land Rover is suitable for a long trip. If you buy a new Land Rover in a wet climate, run it for a few months before setting off on a trip. This allows the wet weather to get at the many nuts and bolts that keep the body together. If these bolts corrode a bit, it will save you a lot of time later. If you take a brand-new Land Rover into a hot climate, you will regularly have to tighten loose nuts and bolts, particularly those around the roof and windscreen.

Early Land Rover diesel engines were not renowned for their reliability. The newer five-bearing crankshaft diesel engines are better, but still underpowered. Land Rover Ltd still refuses to believe that the Third World requires a large, trouble-free diesel engine, and it is sometimes sensible to fit another engine, such as the Isuzu 3.9 litre or the Perkins 4,154.

With the new TDI turbo diesel engines, Land Rover appears to have fixed the problems of its earlier turbo diesel, and owners rave about their good fuel economy. The GRP camshaft timing belt is now 50 per cent wider, but still causes problems in hot, dusty climates, though, to be fair to Land Rover, many modern vehicles have engines fitted with this type of belt and suffer the same problems.

The latest Defenders and Discoverys have five-cylinder diesel engines with a chain drive to the camshaft, so they not only give more power but eliminate the problems of unreliable cam-belts. They are also available with electronic traction control, among other electronic gizmos, although this system is not suitable for Third World use as it is not user-repairable if it goes wrong.

Stretched 127/130 versions of Land Rovers are available, including crew cab versions, but they are underpowered when fitted with four- cylinder diesel engines. Modern Land Rovers do not have double-skinned roofs, so a loaded or covered roof rack is useful to keep the vehicle cooler in sunny climates.

Other 4x4s

The Land Rover Defender's superb axle articulation and lightweight body gives it a distinct advantage in mud, snow and soft sand. If these conditions are not likely to be encountered, then the leaf-sprung Toyota Land Cruisers are comfortable and reliable, though heavier on fuel. Many Toyota models have large overhanging front bumpers, rear steps and running boards, which negate off-road performance. Coil-sprung Toyota Land Cruisers are less reliable, and the latest models with independent front suspension are best avoided. Nissan Patrols lack off-road agility and, as with American four-wheel drives, their large engines are heavy on fuel.

Despite its Paris/Dakar successes, the Mitsubishi Shogun (called Montero in the USA and Pajero elsewhere) has not proved reliable in continuous Third World use. The Isuzu Trooper is not well designed for true off- road work. Suzukis are just too small. Spares for Japanese vehicles can be a problem to get hold of in some parts of the world.

As with Range Rovers, Mercedes Geländewagons have poor load-carrying capacity and their high costs limit their appeal. Several of the latest four-wheel drive vehicles are of monocoque construction, which leaves them without a strong chassis; together with the Suzuki Vitara, Toyota RAV4 and the new Land Rover Freelander, they are not suitable for overland or expedition use.

Four-wheel drive versions are available of most popular pick-up trucks. Those most common in Africa are based on the Peugeot 504 and the Toyota Hilux. The Synchro version of the Volkswagen Kombi has an advanced fluid-coupling four- wheel drive system but poor ground clearance.

Two-wheel drives

The Volkswagen Kombi is in use in almost every country outside the Soviet bloc and China. Anyone who has travelled overland through Africa, Asia, the Americas or around Australia will notice that the VW Kombi is still a popular independent traveller's overland vehicle. Its ability to survive misuse (up to a point) and carry heavy loads over rough terrain economically, while providing the privacy of a mobile home, are some of the factors that make it so popular.

The Kombi has a one-tonne payload and far more living space than a long-wheelbase Land Rover or Land Cruiser. It lacks the four-wheel drive capability, but partly makes up for this with robust independent suspension, good ground clearance and engine weight over the driven wheels. With experience and astute driving, a Kombi can be taken to places that will amaze some four-wheel drive vehicle buffs. The notorious 25 km 'sea of sand' between In Guezzam and Assamaka in the Sahara has ensnared many a poorly driven 4x4, while a Kombi has stormed through unscathed! With the use of lengths of chicken wire fencing, as sand ladders, plus some helpful pushing, a Kombi can get through quite soft sand.

The second most popular two-wheel drive vehicle for overlanders is the smaller diesel-engined Mercedes panel van, which is very reliable. All the stronger rear- wheel drive panel vans are suitable for overland use and most are available with a four-wheel drive conversion. Avoid vehicles that have only front-wheel drive; when loaded at the rear, they often lose traction, even on wet grass in a campsite.

Petrol versus diesel

Weight for weight, petrol engines have more power than diesel engines, but they have several disadvantages when it comes to hard usage in Third World areas. In hot countries there is a considerable risk of fire and the constant problem of vapour lock, which is at its worst on steep climbs, or on long climbs at altitude. Dust, which often contains iron, gets into and shorts out the distributor. High-tension leads break down, and if much river crossing has to be done, water in the electrics causes more trouble. A further problem is that high-octane fuel is not usually available and low-octane fuel will soon damage a sophisticated engine. However, petrol engines are more easily repaired by less experienced mechanics.

Avoid engines with electronic engine management systems. These are not normally repairable if faulty and a flat battery can cause problems with some of these.

Diesel fuel is messy, smelly and attacks many forms of rubber, but it does not have the fire risk of petrol and, outside Europe, is usually one-third of the price of petrol. It also tends to be more available, as it is used by trucks and tractors.

Diesel engines are heavier and more expensive to buy, but are generally more reliable and require less maintenance. An advantage is that extra torque is available at low engine revolutions. This allows a higher gear in the rough, which improves fuel consumption. This means that less weight of fuel needs to be carried for a section without fuel supplies - improving fuel consumption still further. There is also no electrical ignition to malfunction where there is a lot of dust or water. Against this is the fact that diesel engines are noisier and lack the acceleration of petrol engines, which can be tiring on a long journey.

A second filter in the fuel line is essential to protect the injection pump from bad fuel, and a water sedimentor is useful, but it needs to be well protected from stones and knocks.

Some Japanese diesel vehicles have 24-volt electrical systems.

Tyres

Long-distance travellers have to cover several different types of terrain, which makes it difficult to choose just one set of tyres for the whole route. Unless you expect to spend most of your time in mud or snow, avoid the aggressive-tread, so-called cross-country or all-terrain tyres. These have large, open-cleated treads that are excellent in mud or snow, but on sand they tear away the firmer surface crust, putting the vehicle into the softer sand underneath. Open treads tear up quickly on mixed ground with sharp stones and rocks.

If you expect to spend a lot of time in soft sand, you will require high-flotation tyres with little tread pattern. These compress the sand, causing the least disturbance to the firmer surface crust. Today's standard for such work is the Michelin XS, which has just enough tread pattern to be usable on dry roads but can slide about on wet roads or ice. The XS is a soft, flexible radial tyre, ideal for low-pressure use but easily cut up on sharp stones.

As most travellers cover mixed ground, they require a general truck-type tyre. These have a closed tread, with enough tyre width and lugs on the outside of the tread to be good mixed-country tyres, although obviously not as good in mud or soft sand. Such tyres, when fitted with snow chains, are better than any all-terrain tyre for snow or mud use and, if of radial construction, can be run soft to improve their flotation on sand. The best tyres in this category are the Michelin XZY series.

Radial or cross-ply, tubed or tubeless

Radial tyres are more flexible and have less heat build-up when run soft than cross- ply tyres. They have less rolling resistance, thus improving fuel consumption. For heavy expedition work, Michelin steel-braced radials last longer. You must use the correct inner tubes with radial tyres, preferably the ones produced by the same manufacturer. Radial and cross-ply tyres should never be mixed.

Radial tyres 'set' in use, so when changed around to even out tyre wear they should, preferably, be kept on the same side of the vehicle. A further advantage of radials is that they are easier to remove from the wheel rim with tyre levers when you get a puncture away from help.

Most radial tyres have soft side walls that are easily torn on sharp stones, so if you have to drive over such stones try to use the centre of the tyre, where the tread is thickest. For soft sand use, radial tyres can be run at 40 per cent pressure at speeds below 25 km per hour and 75 per cent pressure for mixed terrain below 50 km per hour. Remember to reinflate to full pressure when you return to firm ground. Tubeless tyres are totally impractical for off-road work, so always use tubed tyres and carry several spare inner tubes.

A vehicle travelling alone in difficult terrain should carry at least one extra spare tyre, as well as the one on the spare wheel. Several vehicles travelling together can get by with only the tyres on the spare wheels, so long as they all have the same size and type of tyres for full interchangeability.

Wide tyres

There is a tendency for 'posers' to fit wide tyres. Such tyres are useful in soft sand and deep snow, but in other situations they negate performance. Worse still, on asphalt roads, hard-top pistes or ice they lower the weight per unit area (and hence the grip) of the tyre on the road, leading to slipping and skidding.

Wheels and tyres that are larger than the vehicle manufacturers recommend can damage wheel bearings and cause problems with steering and braking

Never mix tyres of different sizes on four-wheel drive vehicles.

Roof racks

These need to be strong to be of any use. Many of those on the market are flimsy and will soon break up on badly corrugated pistes. Weight for weight, tubular section is stronger than box section, and it should be heavily galvanised.

To extend a roof rack in order to put jerrycans of water or fuel over or even beyond the windscreen is lunacy. The long-wheelbase Land Rover, for instance, is designed so that most of the weight is carried over the rear wheels. The maximum extra weight allowed for the front axle is the spare wheel and a winch. It does not take much more than this to break the front springs or distort the axle. Forward visibility is restricted when going downhill with extended roof racks. Full-length roof racks can be fitted safely, but must be carefully loaded; remember that Land Rover recommends a total roof weight of not more than 90 kg. A good full-length roof rack will weigh almost that on its own.

Expect damage to the bodywork and reinforce likely points of stress, in particular the corners of the windscreen. Good roof rack designs will have their supports positioned in line with the vehicle's main body supports, and will have fittings along the back of the vehicle to prevent the roof racks from juddering forward on corrugations. Without these fittings, holes will be worn in the roof.

Modern Land Rovers have aluminium roof channels, so roof racks fitted to these vehicles require additional supports to the bulkhead at the front and the lower body at the rear.

Nylon or Terylene rope is best for tying down baggage. Hemp rope deteriorates quickly in the sun and holds grit, which is hard on your hands. Rubber roof rack straps are useful, but those sold in Europe soon crack up in the sun. You can use circular strips cut from old inner tubes and add metal hooks to make your own straps. These will stand up to the constant sunlight without breaking. Ratchet straps should not be over-tightened.

In deserts, if one doesn't have a motor caravan, sleeping on the roof rack can be a pleasant way of avoiding spiders and scorpions. Fitting a full- length roof rack with plywood makes it more comfortable, as well as keeping the vehicle cool in the sun. Special folding tents for roof racks are available, at a price.

Conversions

An elevating roof or fibreglass 'pop-top' motor caravan conversion has advantages over a fixed roof van. It is lower on the move, can sleep extra people up top, provide extra headroom while camped and insulates well in tropical heat. Some of the better-designed fibreglass pop-tops do not collect condensation, even when you cook inside them. Some of the disadvantages are that they can be easier to break into, they look more conspicuous and more inviting to thieves than a plain top and they have to be retracted before a driver, disturbed in the night, can depart in a hurry.

In some vans, the hole cut in the roof to fit the pop-top weakens the structure of the vehicle. Driving on very bad tracks can cause cracks and structural failures in the body and chassis; failures that would not normally occur if the vehicle spent its life in Europe. Vans should have roof-mounted support plates added along the elevating roof to give torsional support.

A demountable caravan fitted to four-wheel drive pick-up trucks such as the Land Rover, Land Cruiser or Toyota Hi-Lux could provide a lot more room and comfort, but demountables are not generally robust enough to stand up to the off-road conditions of an overland journey. They also add considerably to the height and width of the vehicle and are more expensive than a proper conversion. Moreover, you cannot walk through from the cab to the living compartment.

Furnishing and fittings

Camper conversions should have fittings made of marine plywood rather than hardboard; it is stronger, more durable and not prone to disintegration when hot or wet. If your vehicle is finally destined for the US, it must satisfy US Department of Transport and state regulations for the basic vehicle and the conversion. The same applies to motor caravans destined permanently for Australia, where equally strict Australian design rules apply to both the vehicle and the conversion.

Most water filtration systems, Katadyn, for instance, are portable and many wall- mounted models can be fitted to a vehicle. On many motor caravans, the water tank and even gas cylinders are mounted beneath the floor, where they are most vulnerable off-road.

Front-opening vents or window quarterlights in the front doors are appreciated in warm climates, as are a pair of fans built in for extra ventilation. However, window quarterlights are attractive to thieves. Fresh air is essential when sleeping inside a vehicle in tropical climates and a roof vent is not enough to create an adequate draught. Equip open windows with mosquito netting and strong wire mesh.

On a long transcontinental journey, one will normally have to do without a refrigerator. (It is often preferable to use the space and weight for more fundamental items such as jerrycans or spare parts.) However, if you are carrying large quantities of film or medicines, you might want to consider using a lightweight dry-operating, thermoelectric 'Peltier-effect' refrigerator from Koolatron Industries, but fit an alternator and spare battery with a larger capacity and a split-charge system.

Stone-guards for lights are very useful, but you need a design that allows you to clean the mud off the lights without removing them (water hoses do not usually exist off the beaten track) and they should not be fitted with self-tapping screws. Such designs are difficult to find.

Air horns should be located away from mud, e.g. on the roof or within the bodywork, where they can be operated by a floor-mounted switch. An isolator may be located on the dashboard to prevent accidental operation of the horn.

For sunny countries, paint chrome windscreen wipers, wing mirrors and any wing steps matt black to stop dangerous reflections from the sun, and have fresh windscreen wiper rubber blades at the ready for when you return to wet climates.

A good, powerful spotlight fitted on the rear of the roof rack will be invaluable when reversing and will also provide enough light for pitching tents. Normal reversing lights will be of no use. Bull bars, also known as nudge bars, are usually more trouble than they are worth, may invalidate your insurance and damage the body or chassis if struck with any force. The EU wishes to ban them.

Paperwork

As well as the obvious requirement for passports, visas and personal insurance, you will require: vehicle insurance for the whole journey, the vehicle registration document, a letter of permission to drive the vehicle if you are not the owner, each of the two types of international driving licences (these vary in the languages of translation) and a carnet de passage for the vehicle. Have photocopies of all of these documents and spare passport-sized photographs. Some countries will insist that you also buy local insurance, but this will only give you the bare minimum of third party cover.

The carnet de passage acts as a passport for the vehicle and is intended to stop you selling it; it will be your largest single expense and is obtainable through the AA or RAC by depositing a bond or taking out insurance. A few countries will note the vehicle in your passport instead of requiring a carnet de passage.

All-important paperwork is best kept in a strongbox that is fixed directly to the vehicle chassis.

Finally, whatever type of vehicle you take and however you equip it, you should aim to be as self-sufficient as possible. You should have food to last for weeks, not days, as well as the tools, spare parts and personal ability to maintain your vehicle and keep it going. Without these, and in spite of the occasional genuinely kind person, you will be conned and exploited to the extent that the journey will become a major ordeal. With adequate care and preparation, however, your overland journey will be an experience of a lifetime.