 Usually, railway vehicle consists of rail car and two bogies. Bogies are the main part of railway vehicle. Usually unnoticed by the passengers, they are very important for safe railway operations. The main functions of the bogies are to support railway body, to ensure stability of railway vehicle on both tangent and curved track, to provide good ride comfort of passengers by absorbing vibrations generated by short and long wave irregularities of the railway track. Bogies can be either motorized, that is, there is a motor on engine embedded in it, or trailed, that is, a bogie without engine. The main elements of the bogie are the frame, the wheel sets and the suspension system. A motorized bogie has additionally the traction motor, wheel gear and transmission system. Here we can see a motorized bogie. Motorized means that the motor is embedded in the design of the bogie. Here we can see the motor. Here we can see the gear box. Here we can see the wheel set. Suspension system. Suspension system of a bogie consists of a primary and secondary suspensions. The primary suspensions connect a wheel set to the frame of the bogie, while the secondary suspensions connect the frame to the car body. Design of the suspension system can differ, depending on the bogie, but the main functions of the suspensions are the same. This is the bolster air spring, the secondary suspension in the bogie suspension system. The secondary suspension is responsible for the comfortable ride of passengers and absorbs the low frequency vibrations of the bogie.