If your plant is among the 70% that use a compressed air distribution system, then you are probably pretty familiar with how air compressors work. But did you know that compressed air is also used to produce, maintain, and even run America’s transportation industry?

Millions of people and products travel by train every day, relying on compressed air to get them from one place to another quickly and safely. In fact, it is compressed air that allows a train to come to a stop.

Air brakes use pressure to tighten the moving railcar’s wheels to a halt. Instead of using brake fluid, like in a car, air brakes use compressed air. Each individual train car contains an isolated tank filled with pressurized air, like that found in the air compressor piping in your manufacturing plant. This reservoir of air is constantly supplying the pressure required to stop the wheels.

In a sense, the brakes are always on. It's the train's default mode. In order to make a train move, the operator just has to disconnect the air tank by pumping air into a separate line called the brake line. This causes a valve to close, separating the tank from the brakes. Once the brake line stops delivering pressure, the valve switches back, reconnecting the air tank and engaging the brakes to allow the train to come to a halt.

Today’s trains are safer than ever before. In the past, a single leak could cause a train to lose all of its pressurized air, making it impossible to stop. Now, runaway trains are much less common. That is because if a train loses all of its air, the brakes automatically activate. If the air tank in just one train car malfunctions, the rest of the train will still run smoothly because each car has its own air tank.

Thanks to innovations in engineering research, today’s world moves significantly faster than it did centuries ago. Though we now have fast cars and even faster airplanes, millions of Americans still rely on train travel, and the freight rail is a $60 billion industry employing hundreds of thousands of people. Without air compressor systems, where would we be today?