Few inventions have had such a strong influence on human life and on the global environment as the automobile. During the past century, numerous technological advances have been made in automobile design, chassis construction, engine power, control systems, safety and emissions-control systems.
The modern automobile is a sophisticated system, with many subsystems having specific design functions. The most basic component is the engine, which produces mechanical energy to move the wheels by turning a crankshaft. This energy may come from the chemical energy of gasoline or electrical energy stored in a battery. How fast the engine turns the crankshaft, and how much energy it sends to the wheels, is measured in horsepower or kilowatts.
Another important part of the system is a suspension that allows the car to absorb the shocks and variations of the road surface, while keeping the tires in contact with it. Most automobiles use independent front suspension, in which the two front wheels are supported independently of each other. The same system supports the rear wheels, making automobile handling smooth and predictable.
A good automobile must also be comfortable to ride in and easy to operate, so that passengers can safely commute to work or school and visit friends and relatives. Automobiles allow people to save time on transportation, compared with using public transit or walking, so they can spend more time doing the things that they enjoy. However, if an automobile is driven unnecessarily or if it is not kept well maintained, it can cause pollution and contribute to traffic congestion.