The side mirrors on an aerial apparatus are primarily used to:

The side mirrors on an aerial apparatus are primarily utilized for identifying obstacles on the sides and rear of the vehicle. This functionality is crucial for safe maneuvering, especially in tight spaces or in dynamic environments like fire scenes, where visibility can be compromised.

The mirrors allow the operator to maintain awareness of their surroundings, helping to prevent collisions with other vehicles, pedestrians, or obstacles that may not be directly visible from the driver's seat. They are essential for operational safety when responding to emergencies, positioning the apparatus, and navigating through challenging terrains, which all directly contribute to the overall effectiveness and safety of the aerial apparatus during firefighting operations.

The other options do not align with the primary purpose of side mirrors; they serve distinct functions unrelated to the visual surveillance of surroundings and situational awareness.