Window tinting looks cool, keeps your vehicle interior cool, or hides your vehicle contents from potential thieves. The drawback with tinting certain windows is that it limits the driver's ability to see and be seen. It is also illegal and may result in enforcement action in the form of either a ticket or a repair order.
One of the rules of defensive driving is to make eye contact with other drivers. A wise pedestrian will also make eye contact with a driver to insure that they have been seen before walking in front of a vehicle. This is impossible for other drivers and pedestrians if you have darkened side windows.
Studies indicate that seniors are particularly affected by window tinting. Their ability to identify and react to low contrast targets is significantly compromised by the light transmission restriction of the film. This applies to a lesser extent to all of us, regardless of age.
The Motor Vehicle Act Regulations are very specific about any film that reduces the light transmitted by a window. You will note that there is no mention of how light or dark the film is. If it reduces the light transmitted in any way, it may only be applied on certain windows of the vehicle.
Film may be applied to the top three inches of the windshield or to any of the side windows behind the driver's shoulders. The film may also be applied to the rear window if the vehicle is equipped with an outside mirror on both sides. Film must not be applied to the windows of the driver and front passenger doors.
Reference Link: http://www.drivesmartbc.ca/equipment/window-tinting-films