New Statistics and Measurements about Glare caused by Headlamps

The new statistics about headlamp glare taken under real traffic conditions for about 4.500 opposing situations during nighttime driving show a percentage of 9,8% with a glare effect with oncoming driver's eyes below the cut-off line inside the active light distribution. The reasons are various like road topography, asymmetric part of the low beam above the horizont, mis-aiming, car inclination by load and often a combination out of these reasons. These glare events can be distinguished in two glare levels called "moderate glare'' and "strong glare''. Out of the 9,8 % of all glare events the strong glare events happen for 1,1 % of all oncoming situations. The majority is in the category moderate glare. The focus of glare reduction should focus on the strong glare events. Technical countermeasures for the strong glare events will also reduce moderate glare effects. On country roads and in urban areas half of the strong glare events are caused by road topography and depend on the vertical radius of the road, the individual vehicle speed, etc. Measurements and simulations are done to create an objective base for the rating of the relevance of headlamp glare and to show up the relation between the acceptance level of driver's and photometric analysis. For typical glare events (glare pulses as "add on'' on the basic glare illuminance) e.g. caused by the topography of the road (vertical radius or bends) the borderline for driver's glare acceptance is at an exposure of H = 2 lx*s. The statistical evaluation of the current glare situation during nighttime driving in combination with the photometric analysis creates a part of the guideline for a measurement based priority list of the most relevant glare effects during nighttime driving.