How far must an employee controlling the movement stop before the last specified distance?

The correct choice emphasizes the importance of maintaining operational safety and adhering to precise stopping distances in railway operations. Stopping at a distance of 1/2 car length before the last specified distance allows for a sufficient buffer to ensure that the train can halt safely and avoid potential collisions or accidents.

When controlling the movement of a train, it is essential to have effective communication and coordination among crew members to ensure the train stops within designated limits. This practice minimizes the risk of overshooting a stop signal or a designated stopping point, which is crucial for maintaining safety protocols on the rail system.

The other options, such as 1 car length, 1 foot, and 1 yard, do not provide the optimal margin needed in most situations, as they either fall short of safety standards or leave too little space for effective control of movement. Therefore, stopping at 1/2 car length upholds a balance between safety and operational efficiency.