What is necessary to prevent movement when leaving unattended locomotives on auxiliary tracks?

To prevent movement when leaving unattended locomotives on auxiliary tracks, utilizing derails or a locked switch is a crucial practice. Derails are physical devices placed on the track that diverts a train from the main track, thereby preventing unintended movement. They serve as a safety mechanism that ensures if momentum is gained, the locomotive will not continue along the intended path but will be redirected.

A locked switch also serves a similar purpose by securing the rail lines in a particular position, making it impossible for the locomotive to inadvertently move onto a different track or route. Together, these measures provide a reliable way to ensure that locomotives remain stationary and do not pose a risk of rolling away, which is essential for safety in train operations. This control over the locomotives helps prevent accidents or unintended movements, especially in areas where personnel might be working or where equipment may be stored.