Why Do Cars Have Mirrors on Both Sides?

The rear view mirror, mounted inside, shows what is directly behind. The driver-side wing mirror shows the left rear. The passenger-side mirror shows the right rear. Each covers a different zone, and together they provide a reasonable picture of the area around the car, though not a perfect one.

A rear view mirror only shows what is behind the car through the back window. Wide vehicles, headrests, passengers, and the angle of view all limit what you can see. Wing mirrors on each side extend your vision to areas the rear window cannot reach.

In early motoring, most cars only had a driver-side mirror or no side mirrors at all. As cars became faster and traffic became denser, passenger-side mirrors became increasingly common. Many countries eventually made them a legal requirement for road safety.

Even with three mirrors, there are still blind spots, areas beside the car that none of the mirrors fully cover. Drivers are taught to check blind spots by physically turning their head before changing lanes. Modern vehicles increasingly use sensors and cameras to help monitor these areas.

The passenger-side mirror is often convex, meaning curved outward, which gives a wider field of view than a flat mirror. The trade-off is that objects appear smaller and further away than they are, which is why these mirrors often carry the warning that objects are closer than they appear.