## 1 Introduction  
Mountainous roads are prone to traffic accidents, especially on sections with combinations of horizontal and vertical curves. According to statistics, approximately 15% of traffic accidents occur on these combined curve sections in mountainous areas [1]. Field research on mountainous roads in central China has revealed that inappropriate roadside plant landscapes can have a negative impact on driving safety. In the surveyed mountainous road sections with combined horizontal and vertical curves, the road facilities are rudimentary, the lanes are narrow, and the distribution of roadside landscapes is chaotic, even obstructing drivers' visibility and leading to traffic accidents [2, 3]. However, reasonable roadside plant landscapes can positively contribute to guiding road alignment, preventing glare, reducing driver fatigue, and enhancing driving safety [4, 5, 6, 7]. Additionally, plant landscapes can beautify the road environment and create a relaxed and comfortable driving atmosphere [5, 6, 7]. Previous research on road landscapes has primarily focused on two aspects. One approach considers landscape architecture and traditional traffic safety principles, such as the \"555\" landscape design principle proposed by scholar [PERSON] [8], emphasizingthe realization of fleeting and panoramic effects, requiring objects in the driver's field of vision to remain for at least 0.5 s, and advocating for changes in the same landscape every 5 min. The other direction explores the deep-seated impact of landscape greening on safety and comfort, focusing on the stability of drivers and vehicles. A scholar such as [PERSON] [9] has combined driving simulation experiments and oral questionnaires to emphasize the driver's driving experience. They found that when the central median and roadside plants are too tall or too colorful, driving stability is at its worst. [PERSON] [10] and others quantified the effects of driving time and roadside landscape colors on the average heart rate of drivers, noting a negative correlation between landscape colors and the average heart rate of drivers, with an increase in brightness reducing driver passive fatigue. There are also many related studies in other countries. Researcher [PERSON] [11; 12] conducted a study on the effects of common Swedish landscapes (open, forest, and diverse) on driving behavior. The results showed that drivers experience less stress and drive faster in open areas. Additionally, combining eye tracking and heart rate tests, the study investigated the influence of roadside object distance on driving behavior. British scholar [PERSON] [13] analyzed the impact of roadside visual environments on driver health and behavior, emphasizing that inappropriate roadside scenery can have adverse effects on drivers. Researcher [PERSON] [14] studied the relationship between road landscapes and driver drowsiness in young males, demonstrating the physiological effects of road landscapes on drivers. Further studies indicate that monotonous roadside environments can cause unpleasant emotions for drivers [15], and plant landscapes can alleviate road rage in drivers [16]. These studies all indicate the significant influence of plant landscapes on This road section is a combination of horizontal and vertical curves in a high-accident area of the S319 secondary road in mountainous areas. Through research conducted by the local traffic management department, it was found that some accidents occurred due to obstructed visibility caused by protruding vegetation on the mountainous, making it difficult for drivers to discern the road alignment. Therefore, it is possible to use appropriate landscaping to guide the alignment of this road section and reduce the accident rate. The research section of the road spans a total length of 1.92 km with a speed limit of 60 km per hour. The horizontal alignment comprises straight lines, transition curves, and horizontal curves, with transition curve and horizontal curve radii of 1500 m and 500 m, respectively.