Train

A train is a vehicle made up of one or more railcars that travel along a railway. Steel wheels fit onto the rails and guide the train while reducing rolling resistance. A locomotive may pull the cars, push them, or both, while others have motors in several cars. Electric trains receive power through overhead wires or, on some railways, a third rail.

Diesel trains use engines that burn fuel to produce the energy needed for movement. Trains can carry passengers, freight, or both, and their design depends on the service they provide. Passenger trains include local and high-speed services. When a train starts moving, its motors produce a force that turns the wheels.

The rails then exert forces on the wheels, allowing the train to accelerate, slow down, and follow the track. Because steel wheels on steel rails create relatively little rolling resistance, a train can move a large load efficiently, although it has much less grip than a rubber tire on a road.

Braking systems therefore play an important role, especially because a heavy train needs a long distance to stop. Modern railways use signaling, track circuits, digital control systems, and other safety equipment to keep trains separated and manage their movements. Rail transport is particularly useful for moving many people or large quantities of goods over land.