OBJECTIVE ASSESSMENT OF THE SAFETY CONTRIBUTION OF TODAY'S AUTOMOTIVE HEADLAMPS
Auto Tech Review|August 2020
OBJECTIVE ASSESSMENT OF THE SAFETY CONTRIBUTION OF TODAY'S AUTOMOTIVE HEADLAMPS
Good lighting makes a major contribution to road safety. In 2011, the International Commission on Illumination (CIE) presented an evaluation system for headlamps that can objectively assess the quality of illumination and glare limitation. New light sources like LEDs and lighting functions (glare-free high beam, partial high beam) have been available for several years, so that an extension of the proven CIE method is necessary, which takes into account, among other things, changed switch-on and service lives of new lighting functions and represents a generally understandable evaluation system. An evaluation system presented in the following by the Technische Uni versität Darmstadt, which was developed by an encompassing expert commission, is intended to provide representative data and enable an objective evaluation of headlamp performance.
DR. JONAS KOBBERT and DR. TRAN QUOC KHANH

MOTIVATION

Statistics show that the risk of accidents at night increases by a factor of 2 to 4 [1, 2]. Good light not only creates a feeling of safety, but headlamps are the main contributors to orientation in nighttime traffic. Particularly since the introduction of xenon and LED headlamps, visibility distances during night-time drives have improved considerably.

In addition to the pure measurement technique for luminous flux and illuminance, the need for a practical evaluation of the safety improvement arose. In 2011, the International Commission on Illumination (CIE) introduced a rating system TC4-45 for headlamps that can objectively evaluate the quality of illumination. Since then, this document has provided an established and precise evaluation system within the circle of experts. The weak point of this evaluation system is the high complexity of individual data, which makes a simple and clear evaluation difficult.

For this reason, a wide circle of European lighting experts has worked on extending the TC4-45 rating system to include glare-free high beam and simplify the rating structure. The working group included experts from Audi, BMW, the Lighting Technology Laboratory of the Technische Universität Darmstadt, Ford, Hella, Lumileds, Marelli Automotive Lighting, Mercedes-Benz, Porsche, Test Center for Lighting Equipment of the KIT, Opel/PSA, Valeo, Varroc, Volkswagen, and ZKW. The first draft, which was presented at ISAL 2019 [3], was improved, provided with additional evaluation options and validated in this working group. The results of this work are presented in this article.

REPRESENTATIVE ASSESSMENT

Current developments on the world market show the need for a clear and representative description of headlamp performance and the contribution to road safety. Various evaluation systems already applied or soon to be announced are neither internationally standardised, nor are some of them practically possible, or only feasible with expensive equipment. Previous analyses show that such test methods are highly susceptible to errors due to the randomness of outdoor tests (vehicle, weather, measurement technology, environment, tolerances) and have no statistical significance due to randomly selected vehicle (tolerances, equipment, condition). The presented evaluation system with the working title Headlamp Safety Performance Rating (HSPR) is supposed to take exactly this aspect of representative evaluation into account.

INCREASED SAFETY THROUGH GLARE-FREE HIGH BEAM

While the previous assessment method standardised by the CIE provides the assessment options for low and high beam, the introduction of glare-free high beam, also known as Adaptive Driving Beam (ADB), has brought an additional safety-relevant lighting function into modern vehicles that cannot be covered by an assessment of low and high beam. The functionality of ADB and the resulting safety gain is documented in numerous studies [4-11]. The work has also shown that adaptive switching significantly increases the usage of the high beam. While with manually switched high beam, the duty cycle is approximately 10 %, an automatically switched high beam increases the usage to approximately 30 % – with the ADB even an average high beam usage of approximately 70 % is possible.

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August 2020