Automobile headlamps are commonly evaluated by calculating physical characteristics of luminous intensity distributions respectively derivated illuminance distributions on the road surface. Especially for road safety one important criterion is the detection distance. Currently it is common to estimate this detection in the distance where an isolux curve (e.g. 1 lx line) is subtending a specified road marking (e.g. right roadway boundary). This approach is quite inaccurate, because many important influencing variables are not taken into account, e.g. object size, contrast or adaptation luminance. Detection distances as well as other criteria could be better predicted if luminance, which is seen by the driver, is used instead. The following article presents a method to obtain sufficient data sets of luminance coefficients for street surfaces to predict background luminances respectively detection distances more accurate than momentary possible. The measuring method was tested in the light tunnel of the Hella KGaA Hueck & Co. in Lippstadt. This data may enable the prediction of luminances, which is not possible today especially for larger distances. With the help of those luminances the adaptation state of the observer can be estimated and the background luminances of obstacles can be determined. With the help of this information threshold contrast models can be applied to predict detection distances for primitive visual targets. So the acquired data set enables an evaluation of headlamps which considers human perception, e.g. visual performance. This permits a comparison of different headlamps in regard to the important criterion traffic security. The current data of luminance coefficients is only valid for the above described geometries. The authors are working on a more general applicable utilization of the data, so that it is possible to vary the position of headlamp and observer. Next measurements will be done for surfaces of real streets. Furthermore it will be tested if the method is applicable for wet road surfaces. The presented work is a first step to obtain so called Bidirectional Reflectance Distribution Functions (BRDF) of road surfaces for relevant angle combinations.
Luminance coefficients of road surfaces for evaluating detection distances
2009
9 Seiten, 4 Bilder, 1 Tabelle, 9 Quellen
Aufsatz (Konferenz)
Englisch
Luminance factors of road surfaces
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