Even small changes in the vehicle inclination, for example due to added load, can lead to changes in the light beam and result in higher glare. The UN-Regulation No. 48 requires a levelling system that has to work automatically for headlamps with a light source emitting a luminous flux over 2000 lumen. The latest development in levelling is dynamic levelling, which is able to compensate dynamic vehicle inclination, for example during acceleration. Besides the 2000 lumen requirement for automatic levelling, there is no further requirement for the dynamic levelling. To propose requirements for dynamic headlamp levelling devices, six representative vehicles with tungsten halogen, high intensity discharge (HID) and light emitting diode (LED) headlamps were examined. These vehicles had different suspension stiffness and were tested empty and with an added load of 250 kilograms. Furthermore, dynamic levelling was deactivated where available, and compared to the activated system. To assess and compare the different headlamps, headlamp levelling devices and load conditions, additional vehicles were placed on the track to simulate oncoming traffic. These vehicles were equipped with photometers and subjects to rate discomfort and disability glare. The results show that vehicle inclination is being influenced by numerous of parameters and only the mandatory use of a dynamic headlamp levelling device can potentially prevent glare. In the second part of the study, the ability of repair shops in aiming headlamps regarding the UN-Regulation requirements was examined. For this reason, the headlamps of two vehicles with tungsten halogen and HID headlamps were misaligned and brought to selected repair shops in order to realign them correctly. After analyzing the data, it was found that headlamps were aimed too low with a mean vertical value of -1.25 percent. (Author/publisher)
Abstract