RD375 - Safety and Visibility Issues Associated with Motor Vehicle Window Transmittance and Aftermarket Window Tinting
The goal of this study was to determine the degree to which after-market motor vehicle window tint films influence individuals’ abilities to see clearly into a stopped vehicle. Three hundred participants viewed the contents and occupants of vehicles from the viewpoint of a police officer making a routine traffic stop. They viewed one of two vehicles in which the front-side windows were tinted to either 50% (current legal standard) or 35% (proposed new standard) transmittance. Viewing was conducted under daylight, dusk, and eight different nighttime conditions typical of those used by officers during a routine traffic stop. This study found that only under certain circumstances, the ability of participants to detect occupants and objects inside a vehicle declined when the level of window tinting increased. In particular, reduced light transmittance negatively affected detection of the driver’s hand positions across all viewing conditions, and reduced object detection during midday viewing. Regardless of tinting level, using take down lights, a spotlight, and a handheld flashlight at night improved performance.