The earliest attempts at producing a self-propelled vehicle date back to the late 1770s. These early vehicles used bulky steam engines for power. Despite constant improvements, the steam engine ultimately proved impractical for small vehicles. The development of the internal combustion engine in the late 1800s provided a small but powerful replacement for steam engines, and was able to achieve much higher speeds. The first practical automobiles were developed in the late 19th century, by automotive pioneers in France, Germany, and the United States. By the 1920s, a number of automotive manufacturing companies were operating in the U.S., including Ford and General Motors. By 1980, more than 300 million cars and 85 million trucks were in operation throughout the world. The popularity of the automobile has led to massive improvements in the highway systems in most industrialized countries. Unfortunately, automobiles are also one of the primary sources of air pollution, and have resulted in an all-time high demand for petrochemical fuels.