From the 1940s to the 1960s, electric and diesel trains replaced steam power in many countries. An electric locomotive uses electric motors to drive the wheels.

Electric trains primarily replaced steam-powered locomotives and, in some specific urban contexts, horse-drawn trams. The transition away from steam was driven by the need for greater efficiency, cleanliness, and power. Steam engines were notoriously inefficient, losing a significant portion of their energy as heat, and they required constant maintenance and massive amounts of coal and water. Additionally, the smoke and soot from steam engines made them unsuitable for the long, enclosed tunnels required for modern subway systems. In 19th-century cities, the earliest electric streetcars replaced horse-drawn omnibuses, which were slow, limited in capacity, and presented significant sanitation challenges due to animal waste. By the mid-20th century, electrification allowed for faster acceleration and higher speeds, enabling the development of the high-speed rail networks we see today. This shift not only revolutionized the speed of travel but also significantly reduced the environmental footprint of the rail industry by eliminating the direct emission of coal smoke and cinders.