When are fusees used?

Fusees are used as both a day and night signal, making them versatile tools for enhancing visibility and conveying information under different conditions. During the day, their bright colors stand out against various backgrounds, while at night, they emit a bright flame that creates a noticeable light source. This dual functionality is essential, especially in situations where train operations may not occur within the confines of standard daylight hours or when visibility is compromised due to weather or other factors.

Using fusees as signals helps ensure safety on the railways by alerting crew members and nearby personnel about special circumstances, such as restricted train movements, track work, or emergencies. Their design and purpose are inherently effective for communication at any time, which is why they are employed regardless of the hour.

In contrast, the incorrect options focus on limitations or scenarios where fusees would not be utilized, thus missing the broader applications of these signaling devices.