Automobiles are a form of road vehicle that use an engine or motor to move but need no horses or other animals to do so. They are usually sized to accommodate one or more people and are capable of traveling over long distances with ease.

Today, millions of automobiles are in operation worldwide, covering over three trillion miles (five trillion kilometers) each year. Their power, speed, flexibility, and versatility have restructured societies around the world. In the United States alone, more than 23 million passenger cars are in operation. Most have an engine that burns a liquid fuel to produce mechanical energy for driving and to provide heat for the interior. This energy comes from the burning of gasoline, but also diesel, propane gas, liquefied petroleum gas, or even solar cells. The automobile’s internal combustion system is surrounded by systems to cool and lubricate its various parts, to control the engine speed, and to deliver electrical energy for lighting and accessories.

The most important component of the modern automobile is its engine, which converts fuel into mechanical energy that drives the car’s wheels. This power is transmitted to the wheels through a transmission, which has multiple gears. Each gear provides a different ratio of crankshaft rotation to wheel-turning torque. Smaller automobiles typically have four-cylinder engines, while larger vehicles require the power of six or eight cylinders.

Most automobiles burn a liquid fuel, such as gasoline, to make their internal combustion engines run. The energy produced by the engine is then used to propel the vehicle through its gears and tires on the road. This process is known as engine combustion, and it produces carbon monoxide, which is a toxic gas. Automobiles have air pollution control systems to reduce the amount of carbon monoxide emitted by their engines.

Cars have revolutionized many aspects of daily life, from city planning and the design of roads to police, fire, ambulance, and utility services. In the United States, Henry Ford’s mass production techniques helped to make automobiles affordable for middle-class families.

For the first time, entire families could take regular vacations and rediscover pristine landscapes. Single people found new freedoms, as well. Women, for example, were able to drive themselves to rallies and speak out for their rights. Nell Richardson and Alice Burke, two of the first women to campaign for the vote, drove across the country in 1916, decorating their automobile with “votes for women” banners. The automobile has become an integral part of American culture, and life seems almost inconceivable without it. The average family now owns more than one car. It is the most common form of transportation in the world. Hundreds of thousands of different cars are made each year, and each one has a variety of systems to support and protect its passengers. These systems include the engine, fuel system, transmission, chassis, suspension, braking system, wheels and tires, and body. These systems are interconnected and designed to support each other.