Automobiles are four-wheeled vehicles that carry passengers and run on gasoline or other fuel. They have been a symbol of both the promise and the pitfalls of modern life. They allow for fast, long-distance travel but also encourage sprawl (sprawling, low-density urban development that degrades landscapes and produces traffic congestion).
An automobile’s engine or motor must provide energy to turn the wheels. This energy comes from either the chemical energy in the gasoline that runs it or electrical energy stored in a battery. The rate at which the engine or motor sends this energy to the wheels is measured in kilowatts or horsepower.
The wheels and tires of an automobile must be able to absorb the shocks of bumping over the road surface and to respond to steering and braking commands from the driver. The wheels are attached to a suspension system, which, like the skeletal structure of a human body, supports the weight of the car and allows it to respond to changes in the terrain.
Many systems are designed to work together to make an automobile operate efficiently and safely, including the engine, fuel system, transmission, cooling and lubrication systems, and electrical system. Safety features, such as tire pressure monitoring and stability control, are required in most countries. Other systems, such as advanced computer technology, improve a car’s performance and comfort but increase its cost. The resulting trade-offs make automobile design a complex balance of many competing factors.