Which component is NOT typically included as part of a vehicle's structural components?

In vehicle design, structural components refer to elements that are essential for the integrity and support of the vehicle's overall structure. These typically include parts that contribute to the vehicle's safety, rigidity, and ability to withstand forces during operation.

The roof, upper tie bar, and frame are all critical components of the structure. The roof helps maintain the vehicle's rigidity and provides safety in events like rollover accidents. The upper tie bar connects various structural parts, contributing to the car's overall strength. The frame, which serves as the main support structure for the vehicle, plays an integral role in absorbing impacts during collisions.

In contrast, side mirrors do not contribute to the vehicle's structural integrity. They are primarily functional components meant for visibility rather than support or protection. Thus, they are not typically classified as part of a vehicle's structural components. This distinction clarifies why side mirrors are the correct answer to the question regarding which component is not included in the structural components of a vehicle.