All states have traffic laws that limit the amount of window tint on motor vehicles—often by specifying the amount of visible light transmission (VLT) that is required. VLT is the amount of light that is transmitted through the window and into the vehicle. For example, a 70%VLT means that 70% of light will pass through the window and 30% will be reflected. Thus, a lower VLT indicates a darker film or tint.

Another term to know is visual light reflection (VLR)—which is the opposite of VLT. VLR is the amount of solar energy that is reflected off the glass and away from the inside of the vehicle.

In most states tickets or citations for illegal window tint are known as fix-it tickets and the ticket or citation will indicate that it is a correctable violation of traffic laws. For example, if you fix the window tint problem within the required period, pay a small fine, and get the signature of an authorized person (a local police officer) the court may dismiss the ticket.

But if you fail to fix the window tint problem within the required period you must pay the fine for the violation and you may be issued another ticket that will be part of your driving record. And if you fail to pay the ticket or appear in court on the hearing date the court may issue a warrant for your arrest.

Window tint laws vary from state to state and some states have exemptions for certain vehicles such as limousines and recognize medical exemptions when the driver has a written statement from a licensed medical doctor, ophthalmologist, or optometrist.

In Illinois, window tint laws are regulated by the Illinois Vehicle Code. The state specifies the amount of visible light transmission (VLT) that must pass through car windows to ensure safety and visibility. For the front side windows, the VLT must be at least 35%, meaning that 35% of the light must pass through the tint. The back side and rear windows can have a VLT of as low as 35% as well, but if the rear window is tinted, the vehicle must have dual side mirrors. The Illinois law also specifies that the front windshield can only have non-reflective tint on the top 6 inches. The reflection for the front and back side windows must not be more than 35%. Illinois recognizes medical exemptions for individuals who require less light exposure; such individuals must carry documentation from a licensed physician or optometrist. Violations of the window tint laws typically result in a 'fix-it ticket,' which is a correctable violation. If corrected within a specified period and verified by an authorized person, such as a local police officer, the court may dismiss the ticket upon payment of a dismissal fee. Failure to comply can lead to fines, additional tickets, and potentially a warrant for arrest if court appearances are missed.