Experimentelle Studie zu Protanopie und Wahrnehmung von Bremsleuchten

The aim of this project is to determine the influence of protanopia (red blindness) on the recognisability of red stop lamps based on an explorative study with test subjects. In the study, a braking situation is simulated at a distance of 15 m from the vehicle in front. This corresponds to a realistic inner-city potentially critical situation at 50 km/h. In order to ensure the transferability of the findings, the legally permitted photometric parameters for stop lamps are chosen as critically as possible with regard to their effect on the recognisability. In the study, a true to scale model of a vehicle rear is placed in front of a vehicle seat with pedals and steering wheel. In the model of the vehicle rear, there are conventional rear lights of a current vehicle with a comparable appearance between both light source technologies, incandescent lamps and LEDs. During the study, four different situations are tested: Day- and night-time conditions in each case with both light source technologies. For each situation, the test subject is presented a set of 20 different bright stop lamp levels with two repetitions in random order. The levels are in the range between 12 cd and 120 cd. As a measure for the photometric evaluation, the luminous intensity contrast between the permanently presented rear position lamp and the respective stop lamp level is used. To investigate perception differences of red stop lamps between protanope and normal vision subjects, the study is performed with the following null hypotheses. H0,1: There is no difference between protanope subjects and subjects with normal vision with regard to the determined contrast thresholds of stop lamps. H0,2: The technologies of incandescent lamps and LEDs used show no difference in contrast thresholds between protanope subjects and subjects with normal colour vision. H0,3: When considering incandescent lamp and LED separately, there is no difference in the reaction time of the determined contrasts between protanope subjects and subjects with normal colour vision. To verify the first null hypothesis H0,1, the perception threshold of the individual contrast levels is determined at a probability of 50 % and 80 %. The perception threshold shows no differences between both groups of test subjects. Considering the variance ranges leads to accepting the null hypothesis H0,1. From the legal regulation requirements UN Regulation No. 7, there is a theoretically minimum luminous intensity contrast between rear position lamps and stop lamps of 4 up to the year 2010 and 2.5 since 2010. The theoretically minimum contrast of 2.5 was recognised reliably by both groups. The second null hypothesis H0,2 tests the influence of the relative spectral distribution of the light source technology, incandescent lamp or LED, on the perception threshold. The technology-sensitive contrast thresholds of both groups of test subjects are compared. The measured contrast thresholds show no differences between the technologies. Thus, the influence of the relative spectral distribution of the examined technology on the perception can be excluded and we can also accept the null hypothesis H0,2. The third null hypothesis H0,3 investigates the influence of the light source technology on the general reaction behaviour in more detail. The determined mean values of the reaction times do not show any differences between both groups of test subjects, also with regard of the presented contrast levels. So, the third null hypothesis H0,3 can also be assumed. Based on the data determined in this study, no safety-relevant influence of an existing protanopia on the perception of stop lamps (UN Regulation No. 7) in road traffic can be demonstrated. It has been shown that there is no difference between protanope people and people with normal vision with respect to the determined contrast thresholds of stop lamps. Therefore, the results of the investigation do not provide a basis for changing the currently applicable legal regulations for driving licenses. Because of the fact that the study was conducted under laboratory conditions, it is not possible to transfer the results in real and complex road traffic. If the results are to be transferred, the determined values are usually multiplied by the so-called practice factor. In this case, using this factor leads to the conclusion that the requirements for stop lamps according to UN regulation No. 7 are not sufficient to ensure a timely detection of the brake light as well as for protanope people and for people with normal vision. Based on this finding, there is a need for further research with regard to the re-evaluation of the minimum and maximum light intensities for the tail lamps and stop lamps respectively their contrast to each other.