Which signal is crucial for alerting crew to a collision risk?

The collision alarm is the most critical signal for alerting a crew to a potential collision risk. This alarm is specifically designed to draw immediate attention to threats of collision, enabling a quick response to avoid an accident. Typically, a collision alarm includes auditory or visual alerts that are unmistakable, ensuring that crew members can react promptly to changing situations.

Other signals, while important in various contexts, do not serve the same direct purpose. Smoke signals are primarily used for communication in emergency situations rather than for collision warnings. Whistle signals may provide acoustic alerts but are generally less effective due to their limited range and potential for misunderstanding in noisy environments. Radio signals are more focused on communications and coordination rather than immediate collision warning, which is the primary function of a dedicated collision alarm. Thus, the collision alarm is essential for ensuring the safety of the crew and the vessel by providing the necessary information to act quickly in the event of a danger.