Which factor would cause a vehicle to fail the mirror inspection?

A vehicle would fail the mirror inspection if the mirror creates interference with forward vision. This is crucial because mirrors are essential for providing the driver with a clear view of the road and any obstacles or vehicles behind them. For optimal safety and control, mirrors must be positioned so that they do not obstruct the driver's line of sight to the road ahead. If a mirror interferes with this forward vision, it can lead to blind spots and increase the risk of accidents, making it a significant safety concern.

While other factors may affect the performance or legality of the mirrors (like being tinted or excessively sized), they do not directly impact the driver's ability to have a clear view of the road in front of the vehicle, which is the primary purpose of the inspection. A convex-shaped mirror, for example, can actually enhance visibility by providing a wider field of view. Therefore, the obstruction of the driver's forward vision is the most critical reason for failing the mirror inspection.