When cars are shoved on a main track or controlled siding, what is the maximum permitted speed?

Answer: A — 20 MPH

The correct response to the maximum permitted speed for shoving cars on a main track or controlled siding is typically restricted speed. This speed is defined as the maximum speed at which a train or a car can safely proceed, considering what is ahead of it. Restricted speed allows for necessary precaution when shoving cars where visibility may be limited, or where there may be a higher risk of encountering other trains or obstacles on the track. In practice, restricted speed usually requires that the train or cars be operated at a speed that permits stopping within half the distance of visibility. This ensures that crew members have adequate time to react and avoid potential collisions or accidents. The other options do not align with the safety protocols established for this scenario, focusing instead on fixed speeds that do not take into account the operational environment typical of shoving movements on main tracks or controlled sidings.