What should be done to prevent movement when securing an unattended train?

To effectively prevent movement when securing an unattended train, it is essential to release all air brakes. This technique ensures that the air brakes do not inadvertently allow any movement due to pressure loss or other factors. When air brakes are applied, they must be properly secured to maintain the train in a stationary position. By releasing the air brakes, any potential issues related to air pressure drops or leaks are mitigated, and the train can be more securely held in place using other methods, such as manual brakes or hand brakes that are less prone to accidental release.

The other options, such as applying head end locomotive hand brakes only, suggest relying solely on one method for securing the train instead of combining several appropriate measures that can increase safety. Only applying emergency brakes is insufficient as emergency brakes are designed for sudden stops and not for long-term securing of a stationary train. Checking for brake pipe leakage, while important for maintenance, does not directly prevent movement. It is a good practice to inspect for leaks, but without initially making sure all air brakes are released, the train may still be susceptible to movement. Therefore, releasing all air brakes is the most comprehensive action to ensure that an unattended train remains securely in place.