[A Comprehensive Look at Rearview Mirrors] 6 Essential Facts About Rearview Mirrors｜How to Choose, Adjust, and Repair Them? Costs? Pros and Cons of Electronic Rearview Mirrors

What is commonly referred to as a "rearview mirror" is technically called a "sight mirror," which is used to observe the rear of the vehicle. However, the term "rearview mirror" has become widely accepted due to habitual usage.

According to Hong Kong’s *Road Traffic (Construction and Maintenance of Vehicles) Regulations* (Chapter 374A), all private cars, taxis, minibuses, buses, trucks, and special-purpose vehicles must have at least two mirrors. One mirror must be installed on the right side of the vehicle's exterior, and the other either inside the vehicle or on the left side of the exterior.

Many vehicles are equipped with a defogging function, which uses heating elements on the glass to remove fog. Some manufacturers also connect the defogging function to the side mirrors, so when the rear window heating is activated, the side mirrors' heating elements will also activate to clear the fog.

Depending on the driver’s height and seating position, car rearview mirrors are adjustable to ensure a clear view of the area behind the vehicle. In the last decade, most car mirrors have been electrically adjustable using a cross-button control. Generally, the correct position for the rearview mirror should be centered on the road's horizon line—not too high (showing too much sky) or too low (showing too much ground)—and should just include the side of the vehicle in the view. Adjusting the central interior mirror is even simpler; it should just show the rear window.

The side mirrors on a car are typically composed of three parts: the mirror housing, the mirror assembly, and the mirror glass. In Hong Kong, due to narrow roads and tight parking spaces, the mirror housing is often damaged. In severe collisions, the entire mirror assembly may need replacement. The mirror assembly contains motors, indicator lights, components responsible for folding the mirrors, and heating elements, so repairs can be expensive. If the mirror housing also needs repainting, the repair cost could reach several thousand Hong Kong dollars.

Replacing just the mirror glass is relatively simple; most mirrors are snapped into the housing. Replacing the glass alone typically costs a few hundred to over a thousand Hong Kong dollars.

To accommodate most drivers, original factory mirrors are usually set to a standard visual angle. However, wide-angle mirror glass is available on the market, offering a broader field of view and being relatively easy to install.

Because wide-angle views can affect your perception of distance, making neighboring vehicles appear further away, it takes time to get used to. If you switch to wide-angle mirrors, ensure you take all necessary safety precautions before changing lanes, such as checking blind spots and allowing sufficient distance and time.

Electronic rearview mirrors replace traditional mirrors with cameras and screens, positioned similarly on the sides of the vehicle and in the central interior. Side electronic rearview mirrors use cameras in the usual mirror positions, displaying the images on screens inside the doors. However, according to *Road Traffic (Construction and Maintenance of Vehicles) Regulations* (Chapter 374A, Section 39), it is illegal to replace mirrors with camera monitoring systems unless exempted and approved by the Transport Department.

Therefore, if you’re considering adding electronic rearview mirrors, it’s advisable to install only the central electronic rearview mirror. This involves mounting a camera on the rear window and connecting it to the central mirror screen, allowing the rear view to be displayed on the screen. The advantages include a wider field of view and a built-in dashcam function.

However, since there is a distance between the camera and screen, it’s recommended to have a professional install the wiring neatly and aesthetically. Installation costs are generally a few hundred Hong Kong dollars.