What does a large X signal by the spotter mean?

A large X signal from the spotter is a universal and clear indication for the operator to stop the apparatus immediately. This signal is critical in maintaining safety during operations, as it signifies that there may be an impending hazard or an urgent need for the vehicle to cease movement. The spotter uses this signal to ensure that the operator is aware of the situation and can take appropriate action to prevent accidents or collisions.

In many operational scenarios, particularly in firefighting or aerial operations, the spotter has a broad view of the environment and can identify dangers that the driver may not be able to see from their vantage point. The large X serves as a visual cue that requires immediate attention and response, which is why stopping is the correct and essential action to take upon seeing that signal. This helps to ensure the safety of both the crew and the surrounding area.