Final answer:
Train operators are instructed to stand when operating a train in the yard because it is easier and safer to maintain balance and adjust to the train's movements. Standing sideways allows them to adjust their body position and counteract the lateral forces exerted on their body.
Step-by-step explanation:
When operating a train in the yard, train operators are instructed to operate from a standing position because it is easier and safer to maintain balance and adjust to the movements of the train. This is due to the distribution of their mass and the forces acting on their body.
When standing sideways, the train operator can easily adjust their body position by shifting their weight from one foot to another or by bending their knees. This allows them to counteract the lateral (side-to-side) forces exerted on their body as the train accelerates, decelerates, or turns.
In contrast, when standing forward, the train operator may find it more challenging to maintain balance and adjust to the train's movements. This is because the forward-backward forces exerted on their body can cause them to lose stability and increase the risk of falling.