The Influence of Side Contour Car Body Lamps on Traffic Safety in Realistic Nighttime Road Environment

Prior research indicates that side collisions account for 31% of traffic accidents, highlighting vehicle visibility as a crucial factor in nighttime traffic accident rates. While adequate side lighting on vehicles could potentially reduce nighttime traffic accident rates, research has yet to confirm this effect, and the optimal lighting parameters remain undefined. This study aims to examine the impact of side contour lamps parameters, including brightness and color, on nighttime vehicle visibility, and propose the optimal light parameters that comprehensively consider the driver's reaction speed and attention load, in order to promote nighttime traffic safety. A total of 22 participants were recruited for this experiment. Participants observed vehicles equipped with side contour lamps completing U-turns on two-way roads under nighttime conditions, performed detection response tasks, judged vehicle visibility, U-turn visibility, and safe forward timing, recorded reaction time by pressing buttons, and filled out subjective evaluation scales. The study compared the effects of side contour lamps at two colors (amber and white), and five brightness levels (10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> cd/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>.<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>.<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>), on drivers' response time and subjective evaluations. The response time results indicated that increased side contour lamps luminance enables participants to detect the side contour lamps and vehicles more promptly. Side contour lamps also aided in recognizing U-turn intentions more clearly, with amber lamps potentially offering advantages over white for detection and safety. The subjective evaluations showed that side contour lamps consistently earned higher ratings for trust, perceived safety, user experience, and system usability compared to vehicles without them. After considering objective and subjective evaluations, the study recommends a luminance level of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>.<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for amber side contour lamps and 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cd/ m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for white lamps. This study provides novel insights into the potential safety benefits of side contour car body lighting, and establishes a foundation for developing relevant standards.