Road transport

Road vehicles of all kindsMotor vehicles of all kinds, including cars, buses, lorries and motorcycles, all have the same basic features. Wheels and suspension allow the vehicle to roll smoothly along the road. Rubber tyres, inflated with air, give a comfortable ride. They also grip the road surface, allowing the vehicle to accelerate or brake without sliding about. Power from the vehicle’s engine, normally fuelled by petrol or diesel, turns the wheels. The exhaust system carries away waste gases. Recharged by the engine, the battery supplies electricity to the engine’s spark plugs, headlamps, radio and other electrical equipment.

Cars

The interior of a carA car is a small wheeled motor vehicle. It carries its own engine or motor and is used for transporting passengers. It usually has four wheels. Saloon cars have a separate boot, hatchbacks have room for luggage behind the back seat, while estate cars have a larger space for carrying extra loads. Some cars are specially designed for speed, including racing. There are about 600 million cars worldwide and the numbers are rising fast.

Fuel

Traffic fumes contribute to air pollution

       










             Most modern motor vehicles are powered by internal combustion engines using either petrol or diesel oil for fuel. Computers are used to ensure the engine runs as smoothly and efficiently as possible. The waste gases given off by petrol- or diesel-fuelled vehicles create air pollution. Today new types of car are produced that use different fuels, such as electricity, biofuels (crops specially grown to be converted into fuel) or hydrogen.

Electric vehicles

Under the bonnet of an electric car

         Vehicles fuelled by petrol or diesel oil give off carbon dioxide in their exhaust gases. Carbon dioxide is a greenhouse gas, which may be contributing to global warming. A “greener” alternative to a vehicle fuelled by petrol or diesel oil is a battery electric vehicle, or BEV. Instead of an internal combustion engine, the vehicle is fitted with batteries that power an electric motor.

An electric car being rechargedThe vehicle is “refuelled” by recharging its batteries. No air pollution is emitted directly by the vehicle, and the silent running of the engine cuts down on noise pollution too. But the vehicles have a smaller range between recharging, and the process may take a long time. Some electric car owners recharge the batteries using rooftop solar panels. While electric vehicles emit little in the way of pollution or greenhouse gas, they use up more electricity produced by power stations.

A hybrid electric double-decker London bus

Hybrids

A hybrid electric vehicle (HEV) combines an internal combustion engine with an electric propulsion system. The vehicles run on electric motors powered by batteries. When the batteries run down, the petrol or diesel engine switches on and recharges them. In some hybrids, the internal combustion engine fires up at high speeds and drives the wheels directly; when the car is slow or stationary, the engine shuts down to avoid kerbside emissions. The first hybrid, the Lohner-Porsche Mixte Hybrid, was invented in 1901 by German engineer Ferdinand Porsche, but HEVs did not become widely available until the Japanese Toyota Prius of 1997. By December 2013, more than 7 million HEVs had been sold around the world.

Lorries

Large haulage lorries are built to carry heavy loads of all types, liquids or solids. They have many wheels, including double wheels on the same axle, to spread the heavy load over a bigger area of road. Many have turbocharged engines (usually turbodiesels) in which air is pumped into the engine to boost its power. They may also have many more gears than cars have, allowing them to cope with all kinds of road conditions.A articulated lorry (tractor-trailer)In an articulated lorry (also called a tractor-trailer), the front part of the lorry, which includes the cab and engine and is known as the tractor unit, is connected to a separate trailer. The trailer may carry a container, a reusable steel box that can be moved from one type of transport to another: ship, train or lorry without unloading or reloading its contents. The coupling is made by a special pivot, in which a king pin on the trailer slots into a U-shaped "fifth wheel". This allows the lorry to turn sharp corners.

Modern lorries often have an aerodynamic shape, to reduce air resistance (drag) and thus save on the high cost of fuel as well as reduce fuel emissions. To help with this, an air deflector or roof fairing, a metal flap fitted above the cabin, guides the air smoothly over the top of the lorry.

Motorcycles

A motocross motorbike rider performs a jump.

Early motorcycles were simply bicycles with a small steam engine attached, but they were not practical machines. The German engineer Gottlieb Daimler built the first motorcycle in 1885 when he fitted an internal combustion engine to a bicycle in 1885 to create the Reitwagen. The first modern style motorbikes, with metal frames, two air-filled tyres and lightweight petrol engines, appeared around 1900. Modern bikes have similar features to cars, but with much greater acceleration.

Most bikes have a chain connection linking the back wheel with the gearbox, which delivers power from the engine. The rider changes gear by depressing a lever with his or her foot. To go round bends, riders must lean into them. The faster they are travelling, the more they have to lean. If they did not, both bike and rider would flip over the other way—and crash.