In what scenario must an outside driving mirror be present?

An outside driving mirror is required to be present when the driver's view to the rear is blocked. This is essential for safety and visibility while driving. When a driver's view to the rear is obstructed by obstacles such as the vehicle's structure or another object, having an outside mirror becomes crucial. It allows the driver to effectively monitor traffic and surroundings, which is necessary for making safe lane changes, merging, or reversing.

The other scenarios do not necessitate the presence of an outside mirror. When parked, a driver may not need to be as concerned about rear visibility. Similarly, driving at speeds under 15 mph does not inherently affect the need for an outside mirror because safety requirements remain consistent regardless of speed. Additionally, relying on outside mirrors only during night driving does not address the general requirement for visibility at all times. Thus, the presence of an outside driving mirror is fundamentally about ensuring safe driving practices when visibility is compromised.