This study analyzes the characteristics of natural lighting and artificial lighting illuminance, correlated color temperature (CCT), and color rendering index (CRI), and their impact on driver visibility. A real-vehicle experiment was conducted to assess visual recognition distances for small targets under various lighting conditions: six levels of natural light illuminance, and artificial lighting combinations of four CCT levels (3000–6000 K) and five illuminance levels (7.5–67.5 lx). Regression models were developed to relate light source characteristics to visual recognition distance. At low speeds (40 km/h), the natural light illuminance thresholds for activating/deactivating road lighting match current standards. At higher speeds (60 km/h, 80 km/h, and 100 km/h), these thresholds increase significantly, reaching 2, 5.5, and 22 times the standard values, suggesting safety risks at speeds ≥60 km/h. The study also finds that visual recognition distance decreases and then increases with rising CCT, with a minimum at 4000 K and a maximum at 6000 K. At 6000 K, the required illuminance thresholds decrease by 52.32%, 47.74%, and 58.31% at 60 km/h, 80 km/h, and 100 km/h, respectively. The research findings provide a reference for optimizing road lighting control strategies, balancing road safety and energy efficiency.
Zhang et al. (2026) studied this question.