Which signal should never be given alongside a red lantern?

In rail operations, a red lantern is universally understood as a signal for "stop." This indicates to train operators or personnel that they must halt their forward motion immediately. Given this primary function of a red lantern, it is incompatible with any signal that suggests movement or proceeding, such as the proceed hand signal.

The proceed hand signal indicates that it is safe to continue moving, which directly contradicts the purpose of the red lantern. If a proceed signal were to be given alongside a red lantern, it would create confusion and potentially lead to dangerous situations on the railway.

Conversely, the stop hand signal, reduce speed signal, and clear signal have defined contexts that can be clearly distinguished from the signals associated with a red lantern. Each of these signals serves distinct operational purposes without conflicting with the imperative to stop when presented with a red lantern, emphasizing the importance of clarity and safety in train operations.