The automobile is a four-wheeled vehicle that is used for passenger transportation. It is usually fueled by gasoline. A number of technical features are also included in an automobile, including an ignition system, suspension, and steering. An automobile is often designed to carry a limited amount of cargo. Occasionally, a vehicle will be designed to carry a large number of passengers.

In the 19th century, inventors such as Richard Trevithick, Nicolas Joseph Cugnot, and Edward Butler patented self-propelled vehicles that were powered by a steam engine. These vehicles were capable of high speeds, but were also inconvenient to start. They also had limited range. After the introduction of the internal combustion engine, the development of an automobile accelerated.

Before the invention of the gasoline-powered automobile, the only self-propelled vehicle on the roads of the United States was a three-wheeled steam-driven car. This design was similar to the Stout Scarab, a car designed by William Bushnell Stout for his own engineering firm.

During the late 1800s, an internal combustion engine was developed that was much more powerful than the steam engine. These engines could go at much higher speeds, and the automobile had begun to overtake the streets of Europe. By 1920, the gasoline-powered automobile had completely overtaken the streets of the U.S. Some of the early automobiles had only one cylinder, while others had chain and sprocket drives.

By the middle of the 20th century, a number of automakers were developing new, sleek iconography and streamlining. Automobiles had become more common as roads and highways were built to link cities and suburbs. In the early 21st century, more manufacturers began adding automatic safety equipment to their automobiles. Computerized driving systems are now available that can completely replace human drivers.

Automobiles are now manufactured with gas-electric hybrids, which utilize a battery-powered electric engine that can be charged with a fuel cell. These automobiles can operate in either an electric-only mode or a hybrid mode, and their speed and range can be improved by using regenerative braking to recharge their batteries. Electric-only cars are typically limited to short trips.

Motorcycles are another form of self-propelled vehicles. Their primary purpose is to provide personal transportation. Compared to automobiles, motorcycles are simpler to maintain and have a smaller number of parts. However, they are not better for traveling on icy roads or in the rain.

Motorcycles can be towed on a trailer by a winching mechanism. If you are going to tow a motorcycle, you should consider how many people you intend to carry. You may need a larger trailer than a car if you plan on carrying a lot of weight. Also, you should make sure the brakes are in good working order.

Many countries have regulations limiting the amount of hydrocarbons and nitric oxides that can be emitted by motorcycles. For example, in 2010, the United States set a limit of 0.8 grams of hydrocarbons and nitric oxide per km for new motorcycles. Since then, more countries have imposed more restrictive laws.