Automobiles are usually four-wheeled vehicles that are propelled by an internal-combustion engine. Gasoline-powered engines are common for passenger vehicles, while diesel engines are used primarily for trucks and buses.

Modern automobiles are made from a variety of materials, including aluminum and titanium. Plastics and other nonferrous metals are also used for components such as cylinder heads and radiators.

A car’s frame is assembled on an assembly line. Then it moves to component assembly areas where complete front and rear suspensions, gas tanks, rear axles and drive shafts, gear boxes, steering box components, wheel drums, and braking systems are installed sequentially.

In the 20th century, automobiles were a major change in American society. Henry Ford’s invention allowed Americans to travel faster and farther than ever before, making it easier to connect with friends and family members across the country.

Vehicles are also useful for commuting to work and school. As a result, they are an essential part of most American families’ transportation needs.

A car can be powered by a gasoline or diesel internal-combustion engine, or by an electric motor that works in conjunction with the gasoline engine. Hybrid vehicles, which combine the advantages of both gasoline and electricity, have become increasingly popular since the early 2000s.

Automobiles are a complex technical system that employs thousands of component parts. Some of the component parts come from breakthroughs in existing technology or from new technologies such as electronic computers, high-strength plastics, and new alloys of steel and nonferrous metals.