Abstract
The purpose of this work is to determine as a function of velocity the minimal roadway luminance that is required to be judged as being bright enough for a driver to perform a nighttime driving task with an adequate feeling of safety. In this context, it shall also be evaluated which areas of the vehicle forefield are most crucial for the driver’s general brightness perception. A field study with 23 subjects and dimmable LED headlights was conducted, in which the subjects were given the task to assess their perceived brightness for different luminance levels caused by the headlights’ low-beam distribution in the vehicle’s forefield on a 5-step rating scale. The experiments were repeated for three different driving velocities of 0 km h−1 (static case), 30 km h−1, and 60 km h−1, respectively. Results for the static case indicate that, for the roadway to be perceived as bright enough by 50% of the subjects, an average roadway luminance of 0.88 cd m−2 is required in an area up to 32 m in front of the vehicle. Furthermore, a significant effect of driving speed is observed. For example, at 60 km h−1, the luminance must be increased to 1.54 cd m−2 to be still perceived as sufficiently bright by 50% of the subjects.
Highlights
The visual system is the driver’s primary source of information in road traffic [1,2,3,4]
As discussed in the introduction section, the literature suggests that with respect to nighttime driving an increased roadway luminance and an improved brightness perception are beneficial for safety enhancement and driving comfort
The study results will be discussed in the following with respect to the initially formulated research questions, i.e., (i) the relevance evaluation of different areas in the vehicle forefield for brightness perception, (ii) the analysis of the functional relationship of the latter with regard to driving speed, and (iii) the determination of an adequate feeling of safety luminance threshold to perform a nighttime driving task
Summary
The visual system is the driver’s primary source of information in road traffic [1,2,3,4]. It is responsible for recognizing and processing important information and dangers at an early stage. Changes in roadway luminance show a significant impact on the safety of driving a motor vehicle in nighttime traffic. Objective parameters, such as accident statistics, and the more subjective perception of safety, are affected
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