When must a vessel reduce her speed according to Rule 19e?

A vessel must reduce her speed when she hears a fog signal from another vessel forward of her beam, as stated in Rule 19e of the COLREGs. This rule is part of the Conduct of Vessels in Restricted Visibility guidelines, which emphasizes the importance of taking preventive actions to avoid collisions when visibility is compromised. Hearing a fog signal forward of the beam indicates that another vessel is nearby and possibly on a collision course, necessitating a reduction in speed to ensure safe navigation and the opportunity to take evasive actions if required.

Other options do not align with the requirements of Rule 19e. For example, operating in clear visibility does not necessitate a speed reduction if there is no risk of collision. Reducing speed only during nighttime operations neglects the fact that vessels may encounter restricted visibility under various conditions, regardless of the time of day. Moreover, a malfunctioning radar does not automatically mandate a speed reduction unless it results in impaired situational awareness, which is covered under other guidance in navigational practices.