Speed controls for traction include not only electrical vehicles of horizontal transportation such as electrical trains , internal - combustion locomotives with electrical transmissions , underground metros , light fait locomotives , trolley buses , even magnetic suspension trains and electrical cars etc . , but also electrical vertical traction systems such as elevators , automatic moving staircases , mine winding engines , and gantry crane trucks etc 牵引调速既包括电气火车、电传动的内燃机车、地下铁道、轻轨机车、无轨电车及磁悬浮列车和电动汽车等这类水平运输电动车辆，也包括电梯、自动电梯、矿井卷扬机和龙门吊车等电动竖直牵引系统。
