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 Wisconsin, window tint laws are regulated under state statutes, specifically Wisconsin Statute 347.10(2m), which governs the permissible window tint on motor vehicles. The law specifies that front side windows must allow at least 50% of light to pass through (50% VLT), while the back side and rear windows can have a tint with a minimum of 35% VLT. The front windshield may only have tint on the top 5 inches or the AS-1 line, whichever comes first, and it must be non-reflective. Wisconsin law also specifies that the window tint must not be more than 35% reflective, which relates to the VLR of the tint. If a driver is cited for illegal window tint in Wisconsin, it is considered a non-moving traffic violation, and the driver may be given the opportunity to correct the violation to avoid fines and further penalties. Failure to correct the issue can result in fines and the violation being recorded on the driver's record. Wisconsin does recognize medical exemptions for window tint; individuals with certain medical conditions can apply for a waiver that allows them to use a darker tint than normally permitted. To obtain this exemption, a written statement from a licensed physician is required.