A modern life would be inconceivable without a means of transportation that can take people to work, school, appointments, and family gatherings. This type of transportation vehicle is called an automobile. There are about 1.4 billion passenger cars in operation worldwide. Most of these are powered by gasoline, but some use liquefied petroleum gas (LPG), natural gas, wood gas, ethanol, or a combination of fuels such as flex-fuel. Some are electric or hybrid.
The scientific and technical building blocks of the automobile are traced back several hundred years to a type of internal combustion engine that was invented by Dutch scientist Christiaan Huygens in the late 1600s. The modern gasoline-powered automobile was perfected in Europe and America toward the end of the 19th century by inventors such as Gottlieb Daimler, Karl Benz, Emile Levassor, and Nicolaus Otto. These innovators used advanced engineering principles to reconcile state-of-the-art design with moderate price. They employed methods such as the assembly line to increase production and lower cost, thereby enabling middle-class families to afford their automobiles.
Passenger cars are the dominant mode of transportation in the United States, where they cover three trillion miles (five trillion kilometres) each year. Automobiles can help people travel long distances more quickly than trains or airplanes, and they can allow people to live in parts of a city or country that are not accessible by public transport. They also give people a freedom of movement that is important in the event of emergencies and for leisure activities such as shopping or visiting friends.
In addition, automobiles create jobs for those who make them and sell them, as well as those who maintain them and provide services like gas stations. They also stimulate other businesses and industries related to the manufacture, sale, and use of automobiles, including road construction and maintenance, car parts manufacturing, and the production of fuels and lubricants. The automobile also opened up new opportunities for women who sought greater independence and could now go places that were previously off-limits to them, such as workplaces, schools, and social gatherings.
Modern automobiles are built with a variety of safety features to protect the driver and passengers, and they are designed for various types of roads, from rural freeways to urban arterials. They are built to have excellent stability at high speeds, with design factors that include the distribution of weight between front and rear wheels, the height of the centre of gravity, suspension characteristics, the choice of which wheels carry power, and the location of brakes. Automobiles are designed for ease of operation, with features such as a self-starter and a closed all-steel body; they can be driven by either the left or right hand. They are often equipped with a radio, air conditioning, heating, and seat belts to improve comfort and safety. Increasingly, they are being made with more environmentally friendly materials. In fact, some manufacturers are producing entirely electric or hybrid vehicles that do not emit any greenhouse gases.