Analysis of Human Intra- and Interpersonal Aiming Accuracy of Cutoff Lines Using Different Adjustment Methods

The result evaluation of the light test carried out annually in German workshops shows that 28.8% of the vehicles tested had a lack of vehicle lighting in 2019. In 8.5% of cases, headlights (SW) were too high and in 8.3% of cases too low. Furthermore, according to the Defect Report 2020 of the Technical Monitoring Association (TÜV), incorrect headlight settings in the main inspection (HU) are the most common cause of failure even in vehicles under three years of age. Incorrectly adjusted headlights have a major impact on road safety, as the headlight setting significantly influences the visibility at night. In the series inspection of many vehicle manufacturers, as well as during adjustment work as part of the vehicle service, a human manually carries out the setting and evaluation of a headlight. This paper therefore examines human adjustment accuracy with the central question of which adjustment tolerances a person achieves. For this purpose, the intrapersonal adjustment accuracy, i.e. the repeatability of a person, and the interpersonal adjustment accuracy, i.e. the difference between individual humans, is investigated by a research study. Therefore, the subjects set cutoff lines with a measuring screen as well as an analog and digital light collection box. The influence of a color fringe and the sharpness of the cutoff lines are analyzed using different headlight patterns. The knowledge gained on human adjustment accuracy should be used to select the most suitable adjustment method in order to optimize the adjustment process of vehicle production and service, as well as to make constructive action recommendations for the design of cutoff lines.