Vehicle headlamps are essential for driver safety at night, and technological evolution of headlamps over several decades has brought substantial improvements to driver visibility and comfort. Nonetheless, glare remains an important concern among many in the driving public, perhaps even more so in North America, where requirements for headlamps differ from those in much of the rest of the world. In most of the world, headlamps producing higher luminous flux are required to have automatic leveling and cleaning systems, thought to help reduce glare. The arrival of headlamp systems in the worldwide marketplace with luminous flux values just below those triggering requirements for leveling and cleaning systems will bring new questions about the causes of and countermeasures for glare. In the present paper, preliminary relationships are described among headlamp and vehicle related factors, particularly headlamp levelness, and the negative consequences of glare, using field data from real-world vehicles and conditions. A better understanding of these relationships could lead to improved strategies for countermeasures to prevent glare, which can be applied to regulatory contexts throughout the world.
