Train

A train is a vehicle consisting of linked cars (bogeys) running on metal rails—two parallel tracks laid down. Train wheels have inner flanges that grip the rails, reducing friction and allowing a small engine to pull heavy loads.

Trains are used to transport passengers and cargo. They vary widely: some connect cities across countries; others operate within cities, such as metro systems and underground railways; and some haul heavy freight and goods for commerce.

Parts of a train

A typical train comprises a pulling engine (called a locomotive) and the cars it draws. In some modern trains, the motor is distributed among the cars, so there is no separate locomotive. Cars are joined by couplers, and the brakes typically operate on compressed air.

Power sources

The earliest commercial trains ran on steam generated by burning coal. In the twentieth century, diesel and electric engines became common. Electric trains draw power from overhead cables or a third rail alongside the track.

Track and special routes

Many countries have built dedicated railway lines with elevated tracks (viaducts) to prevent trains from sinking under their own weight. Systems have also been tested in which the train grips a rail rather than rolling on two rails.