The human visual performance is highly linked to the surrounding and therefore to the adaptation luminance. On roads without street lighting the adaptation luminance is only defined by the vehicle headlamps and the reflection properties of the road surface. For a safe driving during nighttime a minimum of human visual performance is necessary, e.g. to perceive and recognize obstacles in the street scenery in time to enable the driver to start the suitable driving manoeuvre. Aulhorn und Harms published in 1970 a recommendation for the examination of the driver's contrast sensitivity and the relevant limiting values. The results were taken over and published from the German Ophthalmologic Society in a recommendation to examine the driving suitability. Taking into account the development in the field of automotive headlamp technology leading to the introduction of the HID lamp it can be assumed that the luminance distribution on the road surface has been changed. To what extent the defined limited values are affected by these changes was to be clarified in a research assignment for the German Federal Highway Research Institute (BASt) described in the paper. The investigations to determine the contrast sensitivity were separated in two different parts. A large-scale experiment with totally 1701 subjects was conducted to verify the results of Aulhorn und Harms. On the other hand laboratory experiments and experiments with a test car equipped with a head up display were carried out under real driving conditions. A comparison of the results gained with the Mesoptometer at a surrounding luminance of Lu = 0,032 cd.m(exp-2) without glaring and Lu = 0,1 cd.m(exp-2) with glaring pointed out only a mean difference of one contrast step. The statistic verification showed that there is no statistical significant difference of the results, i.e. it can be assumed that under both experimental conditions similar results can be obtained.
Visual performance in the mesopic region
Die Sehleistung im mesopischen Bereich
2003
9 Seiten, 4 Bilder, 1 Tabelle, 3 Quellen
Conference paper
English
Visual Performance at Mesopic Light Levels
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