How often should a sound signal be sounded for a vessel constrained by draft during restricted visibility?

A vessel constrained by draft during restricted visibility is required to sound a signal at intervals of not more than two minutes. This standard is established to ensure that vessels can effectively communicate their presence and intentions in conditions where visibility is limited.

The rationale behind this time frame is to balance the need for safety with the risk of signal fatigue among nearby vessels. Sound signals are an important part of maritime communication, enabling other vessels to be aware of a potentially restricted or hazardous maneuvering situation. If sounds were made too frequently, they could create confusion or desensitization among mariners who are listening for danger signals. The two-minute interval allows for clear and manageable communication without overwhelming nearby vessels.

In contrast, the other answer choices suggest intervals that do not conform to the guidelines as specified in the COLREGs for sound signaling during restricted visibility. Sounding signals every minute or thirty seconds could be excessive, while only signaling at night would not meet the necessary requirements for alertness in all visibility conditions.