Automobiles are land vehicles with four wheels that have an engine or motor that makes them move. They are much faster than walking or riding a bicycle, and can carry more people and luggage than other wheeled transportation. They are also usually easier to operate than airplanes, and can go where other transportation cannot (such as off road). Automobiles are made in many shapes and sizes, and can be used for different purposes. There are passenger cars, cargo, and special automobiles (such as fire, sanitary, autoclave, mobile crane and infantry fighting vehicles).
Automobiles were first developed in the late 1700s and 1800s by inventors such as Leonardo da Vinci and Gottlieb Daimler. Their popularity rose rapidly after the introduction of mass production techniques by U.S. industrialist Henry Ford, which lowered the price of his Model T to an affordable level for middle class families. The automobile greatly expanded freedom of movement for family members. It allowed urban dwellers to rediscover pristine countryside landscapes, and rural residents to shop in towns and cities. Families could drive to recreational destinations with ease, and teenage drivers gained independence that allowed them to explore more options for romantic relationships.
The automobile also ended rural isolation, bringing urban amenities such as schools and medical care to areas that previously had few facilities. It stimulated participation in outdoor recreation, and led to the expansion of tourism-related industries such as service stations, highway construction and motels. It also encouraged new industries such as agriculture and food processing to become more mechanized, enabling farmers to produce crops with fewer human laborers and increase output. The automobile also brought more suburban housing, and changed the way Americans lived, enabling families to spend more time together, and creating new social problems such as traffic congestion, traffic accidents and environmental pollution.
Despite these problems, automobiles continue to be popular, with more than 1.4 billion in operation worldwide, and an estimated three trillion kilometers (five trillion miles) driven on average each year. Most of these are powered by gasoline, which releases carbon dioxide into the air when burned, contributing to greenhouse gasses that contribute to global warming. However, if drivers limit fuel consumption and use alternative energy sources, they can reduce greenhouse emissions.
Other problems associated with automobiles include their high cost and inability to easily maneuver through narrow streets and congested traffic. The safety of automobiles also has been called into question. The increasing number of automobiles on the road have contributed to traffic jams, and their crashes and fatalities have led to demands for licensing and safety regulations. In many parts of the world, public transportation buses, passenger trains and trams offer alternatives to automobiles, and in some cases they are safer and faster than automobiles in heavy traffic.