- Report Published -
|The Effects of Motor Vehicle Window Tinting on Traffic Safety and Enforcement|
|Department of Motor Vehicles; Department of State Police|
|SJR 293 (Regular Session, 1993)|
|All across the United States, the issue of whether motor vehicle window tinting should be allowed and how much tinting should be allowed has been the source of fractious debate in state legislatures. Federal regulations govern all matters concerning motor vehicle window glass for new vehicles. Except for motor vehicle glass that is installed behind the driver in trucks, buses, and multi-purpose vehicles, the glass on all motor vehicles must allow for at least 70% of the light to pass through. However, there are no federal standards that apply to aftermarket applied window tint films.|
There is a demand for tinted window films. The window film industry argues that window tinting creates lower interior vehicle temperatures, minimizes sun-related damage to upholstery and dashboards, provides protection for persons harmed by, or sensitive to, sunlight, and adds some measure of privacy to the vehicle. Also, tinting may enhance the aesthetic appeal of a vehicle, especially when color coordinated with the vehicle's exterior paint.
The enforcement and traffic safety communities, on the other hand, take strong exception to the use of what they might consider excessively dark window films. There is the belief that window tinting may increase the incidence of traffic crashes. Also, dark window films are considered to be a threat to the safety of police officers. There is a desire to afford police officers the opportunity to see contraband or what might be the threatening actions of a person who may be obscured by darkly tinted glass.
In the 1993 Session of the General Assembly, measures designed to change Virginia's laws relating to the application of aftermarket tinted window films to motor vehicle glass were debated. House Bill 1990 (HB 1990), which lessened Virginia's restrictions on tinted glass for vehicles, was passed. As a result, effective July 1, 1993, vehicles are allowed to have window tinting treatments that do not reduce the transmittance of light below 35% for rear and rear side windows and 50% for front side windows. However, no aftermarket tinting may be applied to windshields. House Bill 1436 (HB 1436) also was passed; it allowed individuals with a medical waiver to apply tinted window film on the windshield to reduce total light transmittance to as low as 70% and on other windows to as low as 35% in the vehicles in which they generally travel.
The concerns of industry and the traffic safety community were balanced by the adoption of Senate Joint Resolution 293 (SJR 293). This resolution directed the Virginia Departments of Motor Vehicles (DMV) and State Police(VSP) to "examine Virginia's laws relating to tinted motor vehicle glass and related subjects and the enforcement of these laws and make such legislative and other recommendations as may be appropriate."
The study found that there is no pattern that characterizes the various state laws on window tinting. Virginia's current laws on window tinting are more restrictive than those of 27 states and less restrictive than those of 8 others, with the remaining 14 states having greater restrictions on some windows and less on others. However, the 1993 changes to Virginia's window tinting laws have facilitated enforcement by authorizing the Division of Purchases and Supply to establish standards for equipment to measure light transmittance, which has resulted in permitting the use of a meter to test light transmittance for evidentiary purposes. A survey of 10 state motor vehicle inspection stations revealed that over 80% of the surveyed vehicles that had aftermarket window tinting were in violation of Virginia's new law. The average level of light transmittance on tinted front side windows was 33% and that for rear side windows was 27%.
The study also found that window tinting reduces the ability to detect targets that would be difficult to see through clear glass, and this can be a liability when ambient lighting is low. In addition, the adverse effects of window tinting become increasingly pronounced as transmittance goes below 70%, particularly for people who wear spectacles and for older drivers. There is no evidence, however, that reduced visibility significantly affects drivers' performance during well-illuminated daytime hours. The difficulties are more likely to be manifested at night.
By reducing the amount of light transmittance, window tinting reduces the ability of an outside observer to see into a vehicle, which has led to the concerns about the safety of police officers. However, window tinting also diminishes the ability to see into a tinted vehicle in part by increasing reflectance. Reflected light masks the transmitted light in proportion to the ratio of reflected to transmitted light. Thus, window tinting reduces the amount of light emanating from the interior of a vehicle while increasing the proportion of light reflected off of its surface from the outside. Unfortunately, because the disruptive effects of reflections are situationally specific, it is not possible to determine whether Virginia's new laws compromise the safety of police officers.
On the other hand, window tinting can reduce discomfort glare, which is the unpleasant feeling that accompanies exposure to a source of glare. Further, window tinting films do not reduce contrast. Since window tinting films reduce transmittance proportionately, the target/background contrast is constant across all transmittance levels. Also, window tinting has been shown to reduce vehicle interior temperatures.
Although there are only limited optical benefits to be derived from window tinting and there are a number of potential optical detriments, there is no empirical evidence to indicate that the tinting allowed under Virginia's current laws creates a safety hazard in terms of driver performance. Thus, it is recommended that Virginia's new laws on window tinting not be changed unless compelling evidence that the standards compromise safety is found in the future. However, further research is recommended on the effect of window tinting on facial communication, the performance of drivers, and the safety of police officers.
It is also recommended that federal regulations and/or action by the states to achieve national uniformity be encouraged in order to promote uniformity in laws and regulations concerning aftermarket window tinting. Such action would remove the burden of changing applications of window tinting by military personnel and other individuals who relocate from one state to another.