Background and Objective: The number of road accidents and casualties is considerably high in Iran. In addition, car headlights, especially on two-way roads, cause glare in the eyes of oncoming drivers. This study aimed to determine the level of discomfort caused by the glare of car headlights and the effects of some variables on creating discomfort glare.
Materials and Methods: The illuminance of the driver’s eye was measured using luxmeter, and the severity of discomfort glare caused by the car’s headlights was determined using the Schmidt-Clausen and Bindels model, the lateral and longitudinal distance between the two vehicles, and the background luminance of the road surface.
Results: In the low beam mode of the cars, luxmeter failed to record any illuminance from 100 to 50 meters distance. In the high beam mode, the discomfort glare gradually increased by the reduction of the longitudinal distance between two vehicles from the distance of 100 meters. Increase in the level of discomfort glare for Samand, Pride Saba GTX, Pride 131SL, Renault Megan, and Peugeot Pars cars continued up to 30, 20, and 10 meters, and up to 10 and 20 meters in the case of Peugeot 405 car depending on the background luminance, respectively. The level of discomfort glare reduced from these intervals onwards.
Conclusion: The discomfort glare can be affected by changes and adjustments made in the side distance between vehicles, direction and height of car headlights, as well as voltage and type of headlight lamp and can be reduced by changes in road design and vehicle headlights.