Final answer:
In an emergency, the train operator should apply the emergency brakes to stop the train before reversing the motors. Standing close to railroad tracks is dangerous because the passing train can create a low-pressure area that pulls you toward it.
Step-by-step explanation:
If it is necessary in an emergency to reverse the motors of a moving train when the controller is in an ON position, the appropriate action for the train operator to take is to apply the emergency brakes. This is a safety measure to ensure that the train does not continue moving uncontrollably in one direction while trying to reverse the motors, which could lead to further complications or hazards. After the train has come to a complete stop and is stationary, the operator can then safely reverse the motors and proceed in the opposite direction as required.
In regard to the additional question regarding the danger of standing close to railroad tracks, it's explained that atmospheric pressure can push you toward the train due to a phenomenon where the train displaces air as it passes, potentially creating a low-pressure area behind it. This pressure difference can cause a person standing too close to experience a force pulling them towards the train, which is why it is dangerous to stand near a rapidly moving commuter train.