PADave,
What they are doing.
A ground employee, conductor or brakeman, is going in between the cars or between the locomotive and the cars.
Three step, (down here called the Red Zone) prevents the engineer from moving the train or the locomotive with the employee in a position to be harmed by the moving equipment.
He or she may be lacing up air hoses, cutting in the air, (opening an anglecock) or tying/taking off a handbrake, all tasks that require the employee to be out of sight of the engineer and in between the equipment.
Only the employee who requested the three step protection or Red Zone may release it, and no one may “piggyback” on someone else’s protections.
In other words, if I request three step, only I may enter the danger zone on that request, my helper has to ask for his own protection, which the engineer also has to acknowledge, so that if I clear myself, and the helper has not, and I tell the engineer to move the train, he may not do so until the helper releases his protection.
As was pointed out, it requires the engineer to apply the train brake and the independent brake, center the reverser, and put the generator field switch in the off position.
With this done, it prevents the alternator (they don’t use generators anymore) from providing current to the traction motors, even if the throttle is moved, and because both the train brake and the independent brakes are applied, and the reverser is centered, (neutral position) the train can not move under it’s own power.
Each one of these steps should disable the locomotive and prevent movement each on its own. Combined, it requires the engineer to do several steps before he can move, which requires him to think about what he is doing.
Trust me; nothing is more terrifying that having a train you are lacing up or knocking a brake off of suddenly move, you learn to jump mighty quick and mighty far!
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