Trains are one of the most popular transportation systems because they are cost effective and able to transport lots of people or goods. Trains also provide high-speed transportation with relatively low CO2 emissions. A train can be a combination of one or more locomotives and attached railroad cars or a self-propelled multiple unit. A modern train is usually powered by grid electricity or by diesel locomotives. Trains have become more sophisticated with advanced systems that automatically control and monitor train operation. These integrated systems give passengers and freight a smooth and safe ride. This white paper discusses how modern train system design ensures reliable operation of the train power source, propulsion system and coach control systems.