Some people call it the tube, some know it as the metro, and others call it the underground. You might know it as a subway. All these terms refer to an underground railway system of connected cars that transport people from place to place in cities and suburbs.

Subway passengers board or exit the cars at stations along a route. Steps or escalators usually connect a subway station to the street level. Some subways emerge above ground at the far end of a line. Most subways pass under city streets, but they can also pass under rivers or even ocean bays.

The first subway, in London, was begun less than two hundred years ago and finished three years later. Workers dug trenches below the streets, built bricked sides and arches in the trenches, and then covered them with earth and restored the streets to their original condition. The first subway line used steam locomotives. This new way to travel was an immediate success, carrying more than nine million passengers during its first year.

A few years later, another subway line was begun in London, using a special tunneling shield that pushed through the clay deep underground so that street traffic wasn’t disrupted. On later subways, electricity was being used to operate the lines.

Other cities began to build subways. The first subway line in the United States was constructed in Boston and was completed about one hundred years ago. A few years later, New York City began what was to become the largest subway system in the world.

In the twentieth century, developers began using computer and aerospace technology to build automatic subway trains. The first completely automatic system was developed in the San Francisco Bay area. This system is operated by remote control. Most of today’s subway cars have air conditioning and offer smooth, fast rides.

When you consider the problems caused by increasing traffic on city streets, subway travel makes good sense. You’re doing your part for clean air, you’re avoiding the bother and risk of car travel, and your attention is free for reading or daydreaming. The subway is a smart way to go.