The effects of Xenon-HID and Daytime Running Lights upon health



Effect of DRL on the eye





What's New

Action Centre



Views on DRL from:







Related Health pages:

Medical Letters

Glare and Distraction repo






Updated 13 December 2010


Glare and Distraction - also see Ophthalmological reports in Studies


Visible light is one portion of the electromagnetic spectrum ranging from radio waves with wavelengths of a meter or more, down to x-rays with wavelengths of less than a billionth of a meter.  Optical radiation lies between radio waves and x-rays on the spectrum, exhibiting a unique mix of ray, wave, and quantum properties.  At x-ray and shorter wavelengths, the electromagnetic radiation tends to be quite particle like in its behaviour, whereas toward the long wavelength end of the spectrum the behaviour is mostly wavelike.


White light is a form of radiation ranging from infra red with a wavelength of 770 nanometres to ultraviolet with a wavelength of 380 nanometres. Beams from a motorcar headlamp directly focus this radiation into other driver’s eyes, even indirectly when dipped, the reflector is visible.  The blue end of the spectrum from Tungsten Halogen lamps and particularly the more glaring Metal Halide Xenon High Intensity Discharge (HID) lamps can cause “starring” glare and dazzle severely reducing a driver’s field of vision.   "Automotive HID burners do emit considerable near-UV light, despite the shield" - Wickipedia


Whilst manufacturers will maintain DRL from dipped beams should not dazzle, they can cause dynamic glare due to road undulations, speed humps, acceleration, vehicle loading or headlamp misalignment.  HID headlamps are increasing on vehicles, these emit light radiation in the more harmful blue/ultra violet end of the spectrum.  EU law requires self levelling mechanisms. but these have insufficient reaction speed or dip range to cater for rapid vehicle movement thus adding to glare.


As the demographic age of the UK's population changes to "grey power", more, older drivers will be using our roads.  These drivers are more susceptible to glare; many drivers simply do not drive at night. When all vehicles are forced to use DRL by EU directive, the effect of daytime glare to this age group will have negative safety results.



As a person ages, the incidence of cataracts (in the eye's lens) increases.  This causes increased sensitivity to glare. Unlike the theory behind proclaimed benefits to DRL and Xenon-HID, the sensitivity of a person with cataracts to glare is a proven fact. Research shows a percentage of people who have had laser eye surgery will become more glare sensitive.  As more and more middle-aged and elderly use laser eye surgery rather than glasses, this danger will grow.



Whilst in the short term, drivers using DRL may claim less people run into them, when every one uses DRL or Xenon-HID, the benefit will be negated and our roads will become more dangerous, particularly for motorcyclist, cyclists and pedestrians.  We see the problem compounded by irresponsible advertising by motor manufacturers that shows cars with all lights, including fog lights ablaze in good daylight.  This is in contravention of the UK Highway Code.


Change blindness

Any 'overaccentuation' ie. DRL in a visual field (especially moving  bright stimuli) are attracting attention.  The eye is forced to fixate these objects thereby distracting attention from less prominent objects.  No 'scientific' study will be able to disprove these facts.

Change blindness, inattentional blindness, amnesia, crowding phenomena, multitask problems, interference of too many inputs worsen the situation additionally.

Blinding white LED's used by some Auto manufacturer's are usually adapted from the eye damaging Blue Ultraviolet end of the spectrum.


This is why certain manufacturers using ultra bright LED's  will eventually be forced to recall their models fitted with LED DRL.


Typical White LED spectrum


Chromatic Aberration - Visible Blue and Ultra Violet Light - Hazard from High Intensity Discharge headlights

Blue and violet light has high energy and high phototoxicity  causing temporal summations, increased glare, straylight, reduced contrast vision and Chromatic Aberration.


Within the eye, there are no blue cones in the central retinal area, blue rays focus in vitreous body therefore blue light does not improve central vision.
A Yellow Filter (420 - 450 nm cut off headlights, streetlights etc.) might improve contrast vision, reduce glare and straylight.

Critical Intensity: Worst example: modern headlights: some are too bright at the 'Vorfeld' (area within 40m in front of the car,) causing adaptative problems and glare for the drivers. Traffic relevant objects at greater distance might virtually 'disappear'.

Critical number: Repetitive retinal light 'stress' could cause transient dysfunction or de-compensation (prolonged retinal recovery times)
Too many light stimuli simultaneously moving across the visual fields might cause capacitive de-compensation of cognitive processing Visual Short Term Memory (VSTM), change blindness, inattentional blindness, sustained inattentional blindness, repetitive blindness etc.).

Other distracters like advertising illuminated signs etc. induce additional over-stimulation and irritation thereby provoking inadequate reactions of drivers.

Resumé: Stimulus parameters (single stimuli and/or sum of all different stimuli),  quality  (e.g. spectrum), intensity and number must not go beyond the scope of physiological borders of sensory organs and exceed the limits and the capacity of cognitive central nervous processing.

Conclusion: avoid over-dosage of intensity and transgression of the critical number of stimuli, reduce 'crowding' and distractors in traffic scenarios.



Light stimuli attract attention.  This holds true for Daytime Running Lights (DRL), especially whenever light stimuli as such are moving across peripheral areas of the visual field. DRL is causing improved conspicuity of DRL-vehicles thereby withdrawing attention from ALL other traffic relevant objects.  As prognosticated - this unwanted and undesirable side-effect of DRL is causing an increasing number of traffic accidents. Unfortunately at the cost of 'weaker' traffic participants, especially children.

In order to prevent  more accidents and fatalities in future any kind of lighting in bright daylight has to be avoided. Worldwide. The use of headlights under daylight conditions appeared to be even more contra-productive than DRL. Glare and irritations caused by stray light and reflections together with 'overflow' and de-compensation of  visual short term memory intolerably reduce the general traffic safety. Global warming - as a symptom and a warning - predicts useless and dangerous waste of energy.  Univ. Prof. Dr. Peter Heilig

See letters from the medical profession and glare and distraction reports which warn of the dangers of dazzling lights.

The Austrian Ophthalmologic Society bans daytime running lights - English  German

Accentuating one group of 'traffic-relevant objects' makes all the other objects less conspicuous - worst case - they might turn into sub-threshold stimuli hence escaping attention - to be overlooked .....


In analogy to the Hippocratic oath some particularly conscious scientists swear a voluntary oath:


"I promise to work for a better world, where science and technology are used in socially responsible ways. I will not use my education for any purpose intended to harm human beings or the environment. Throughout my career I will consider the ethical implications of my work before I take action. While the demands placed upon me may be great, I sign this declaration because I recognize that individual responsibility is the first step on the path to peace." Heather Stewart


"First, in all my scientific work I will be honest and I will not do anything which in my view is to the obvious detriment of the human race. Second, if later I find that my work is being used in my view to the detriment of the human race I will endeavour to nullify these developments." Peter Reineker


„Ich schwöre, dass ich meine Erkenntnisse, meine Erfindungen und die Anwendungen, die ich möglicherweise daraus ziehe, niemals in den Dienst der Gewalt, der Zerstörung oder des Todes, der Vermehrung des Elends oder der Unwissenheit, der Unterdrückung oder der Ungleichheit, sondern ausschließlich der Gleichheit unter den Menschen, ihres Überlebens, der Verbesserung ihrer Lebensverhältnisse und der Förderung ihrer Freiheit stellen werde.“ Thesaurus der exakten Wissenschaften. Serres & Farouki (Ed). Zweitausendeins. Frankfurt


The ' experiment' Daytime Running Light/Licht am Tag (DRL/LAT) in Austria is not in accordance with any of the oaths cited above. It violates the rules of the exact sciences. It contradicts common sense and is unethical. Moreover, it implies a Violation of the Obligation of Protection.


DRL/LAT was designed in order to improve the safety of all participants in traffic - without any exception. However,  the focus on only one particular group by DRL/LAT, namely on cars, inevitably makes all other persons and objects involved in traffic less conspicuous and thus exposes pedestrians (especially children), cyclists, bikers, handicapped persons, wheelchair-drivers, etc., to more hazards.


At the end of the observation period of [approximately] one year the foretold increase in the number of traffic accidents (involving predominantly children) at pedestrian crossings could be observed. In Clinical Studies the FDA [Food and Drug Administration] would immediately interrupt an experiment yielding such counterproductive and fatal results. Advocates and supporters of DRL/LAT claim that this measure reduces the total number of traffic accidents. For many reasons a merely statistical approach is highly questionable. Light stimuli moving in central areas and even more on the periphery of a visual field automatically attract attention and thereby obliterate any other object. However, the visibility of all participants needs to be enhanced if traffic should be safer. Furthermore, the visibility should be improved by 360 degrees, i.e. on all four sides; if not, this means that the flanks of a car, for example, become less noticeable and the total concept will break down To ignore or neglect particularly vulnerable  or unprotected participants or parts (see rear-or side-impact crashes) would create a situation resembling that of ‘blind spots’ [i.e: The failure to enhance the visibility of unprotected  participants and parts inevitably will create blind spots]. Accidents caused by the failure to notice other participants in traffic therefore may even endanger DRL/LAT-drivers in the long run.


*Only front daytime running lights are requested in Austria. In accordance to the new regulations or amendment no rear lights are requested during daytime.  


 Statistical analysis: No significant results can be expected. No conclusions are allowed. Why? First of all, the prerequisite, the homogenous matching group is lacking. 'Mixed traffic' (the worst and least desirable situation ever - Bergisch Gladbach 2005) comprising inhomogeneous and inconsistent data had to be evaluated. Dipped (or not..) headlights, daytime running lights, blinking diodes and un-'accentuated' objects, resting or moving in changing formations were comprising the group before DRL/LAT. Innumerable other parameters like weather-influences, economy, road-constructions, tunnel-illuminations,  ‘roundabouts’, traffic-signs and -lights, road repairs, street lighting, traffic regulations, fine praxis etc. varied and changed throughout the time spans corresponding. Choosing a single parameter (DRL/LAT) out of many and constructing faulty and incorrect causal chains will never vindicate and justify a worldwide lucrative branch in industry: The DRL/LAT-production.


Undesired side effects of DRL/LAT: 'Change Blindness, Inattentional Blindness, Inattentional Amnesia (Computer Simulation: Motion Induced Blindness' - a related phenomenon), disturbances of the 'gist' of the traffic scenario and of the equilibrium of concentration, ‘near misses’ with following imbalances of vigilance and attention, crowding, 'overwriting' and functional deficits of Visual Short Term Memory (VSTM),  failures of apperception and perception, glare and overexposure (headlights during daytime), temporal retinal summations, phototoxicity, prolonged retinal recovery times (Macula 'Stress'-Test), over-stimulation and over-strain, insufficient signal to noise ratio of DRL/LAT (..toward zero in bright daylight and sunshine), lack of automatically shutoff systems at the gates, at red traffic lights etc., increasing percentage of maladjusted, defective and blind headlights (‘one-eyed’), blind rear lights (even in  tunnels - drivers are inclined to forget), side impact crashes, repair costs, pollution, waste of energy, light pollution, economy, ecology, environment, an incomplete though never ending list..


An advantage/disadvantage DRL/LAT analysis would be instructive. Unfortunately due to the dynamic complexity of this subject no significant result can be expected, similar to intended comprehensive statistical analysis. Comparable to other countries with DRL/LAT-regulation the number of traffic-accident-victims in the 'weaker' group of traffic participants (children in the first line) is constantly growing, unfortunately, unpardonably.


Northern countries (and regions in the extreme south correspondingly): Geography has no influence upon the laws of sensory physiology, cognition psychology, brain research etc. Distraction and distracters (DRL/LAT) are causing similar and identical disturbances of vision, perception, apperception, orientation and proper reaction - all over the world. DRL/LAT is not indicated. There is no need for DRL/LAT.





DRL/LAT- induces interferences and disturbances at any level of background light intensity - at any time - at any location in geography. Reflectors and reflecting clothing cannot be 'activated' by DRL/LAT - no light beam can cause the desired reflections in order to enhance the conspicuousness of 'traffic relevant' objects. No scientific argument and no statistical analysis can justify the use of DRL/LAT. Definitely not at the cost of victims in traffic accidents.


Headlights: To be used only under conditions of reduced sight (dawn, dusk, reduced daytime-light-intensity, fog, deep shadow). Exclusively the use of appropriate headlights (glare-free) at the proper situation can allow better and earlier perception, apperception and recognition of 'traffic relevant' objects. This conception represents the only sensible and scientifically acceptable way to higher safety in traffic - for everybody.



'Field Studies and Scientific Experiments': An Ethic Commission and a Science Commission - like a pendant to the FDA should prove thoroughly, conscientiously and scrupulously any new 'idea' or proposition in traffic policy forcing immediate interruption of regulations like DRL/LAT which are leading to undesired and even fatal results.


Daytime Running Light = Licht am Tag (DRL/LAT).