Influence of dirty headlamps on straylight and glare

Authors: Dr.-Ing. Christoph Schiller, Dr.-Ing. Dmitrij Polin, Kyriakos Kosmas MSc., Prof. Dr.-Ing. habil. Tran Quoc Khanh

There are two main reasons, why clean headlamps are essential for traffic safety – dirty headlamps reduce driver’s visibility distance and moreover they glare other road users. Therefore ECE regulation No. 48 prescribes a headlamp cleaning system. But this rule is limited to “dipped-beam headlamps with a light source or LED module(s) producing the principal dipped beam and having a total objective luminous flux which exceeds 2000 lumen” [1].

In recent years LED headlamps are increasing their market shares. They are enabling extremely efficient front lighting systems with HID performance while using less than 2000 lm for the dipped beam. Due to limited space in the motor compartment and the efforts to increase energy efficiency by reducing the total vehicle weight and to reduce the total costs car makers tend to economize on the headlamp cleaning systems.

Keeping in mind, that LED headlights with possibly less than 2000 lm get more and more common on the market, the aim of this paper is to show the effects of dirty headlights on straylight and therefore on the potential of glaring other road users.

At the Laboratory of Lighting Technology of the Technische Universität Darmstadt, we used a vehicle with deactivated headlamp cleaning system such as no cleaning system would be available. With this prepared car we drove on different roads during winter time to have a scenarios for soiling the headlamps in a realistic way. In order to reduce possible risk for the driver (reduction of visibility distance) and other road users (glare) these tests were performed during daytime.

This paper outlines and discusses the findings of the conducted study regarding horizontal cut-off lines (dipped beam with HID and halogen tungsten lamps) as well as vertical cut-off lines (glare-free high beam, ADB). Straylight in the area around the B50 L point and the illuminance levels around the B50R point are measured with dirty and clean headlamps and the measuring results will be analyzed.

[1]Regulation No 48 of the Economic Commission for Europe of the United Nations (UN/ECE) — Uniform provisions concerning the approval of vehicles with regard to the installation of lighting and light-signalling devices, L 323/46, 6.12.2011.