Optimal Configuration Research of Plant Landscapes under Combined Horizontal and Vertical Curves on Mountainous Roads

The combination of horizontal curves and gradients can lead to visual perception errors by drivers, resulting in risky operations. While plant landscapes serve to guide road alignment and alleviate driver stress, irrational plant landscapes can obstruct the driver’s view, leading to traffic accidents. This study aims to explore the optimal configuration of plant landscapes on horizontal–vertical curve sections. The standard deviation of speed and lateral displacement were selected as two important measures of vehicle stability, and four crucial factors of plant landscapes were identified: color, height, roadside distance, and plant spacing. Subsequently, Design Expert 10, UC-win/Road 16.0 software, and a driving simulator were employed for scene design, modeling, and driving data acquisition. The Box–Behnken Design response surface method was utilized to analyze the influence of plant landscape factors on vehicle stability and predict the optimal configuration of plant landscapes on horizontal–vertical curve sections. Finally, validation experiments were conducted. The results indicate that the height and spacing of plants significantly affect vehicle speed, while plant height and roadside distance significantly impact vehicle lateral displacement. Through validation experiments, it was confirmed that the optimal plant landscape configuration is green in color, with a height of 4 m, a roadside distance of 1 m, and a plant spacing of 10 m. Therefore, rational plant landscapes can enhance driving stability and are essential measures for improving traffic efficiency and safety.