Automobiles are one of the most common forms of transportation. Around 1.4 billion cars are in use worldwide, one-quarter of which are found in the United States. Each year, Americans drive approximately three trillion miles. The automobile industry has seen significant growth over the past few decades, with more manufacturers introducing new designs to the market.
Automobiles are self-propelled vehicles that can carry a number of passengers. Motorcycles, however, do not fall into this definition. They have three wheels and are not capable of carrying many passengers, although they do have side cars. Several court cases have ruled that motorcycles are not automobiles.
Automobiles make use of advanced materials to improve durability and safety. The frame and wheels of automobiles are made of steel or aluminum, and the wheels are typically steel with spokes. Some motorcycles have cast steel wheels. Automobiles are also equipped with a variety of safety features, including airbags.
The earliest automobiles were built in the late 1800s. The earliest cars had manual transmissions and had to be pushed by a driver. Some of the first cars used gasoline. The modern automobile was designed by German engineers in the late 1800s. Nikolaus Otto, a co-founder of the Deutz Gasmotorenfabrik, claimed to have built the first motorcycle in 1872.
Modern automobiles are designed to accommodate many passengers. Most have four or five seats, but larger vehicles with more than seven seats are referred to as limos, SUVs, buses, and minivans.