If the master controller is returned to OFF but the motors continue to take power, what should the train operator do first?

In this situation, the correct action for the train operator is to open the control switch. The master controller is designed to cut off power to the motors when it is set to the OFF position. However, if the motors are still taking power despite being turned off, it indicates a fault or malfunction within the system or controls.

By opening the control switch, the operator immediately disengages the power supply to the traction motors, providing a quick and safe response to an unexpected situation. This action helps to protect both the train and its passengers from potential damage or danger. It effectively ensures that the train is brought under control before any further action is taken, such as investigating the cause of the malfunction or contacting the dispatcher for assistance.

Engaging the circuit breaker or reducing throttle would not be prudent first steps in this scenario, as they may not address the immediate issue of the motors receiving power when they shouldn't be. Contacting the dispatcher is also a necessary step eventually, but should follow the immediate action of ensuring the safety and control of the train.