## 6 Conclusions  
In conclusion, this study addresses a significant research gap in the industry by quantitatively analyzing the rationality behind the design of landscape elements in urban tunnel cavern sections. By investigating the influence of different combinations of landscape elements on driving safety and comfort, we propose an innovative methodology for evaluating the design of these elements in urban tunnel cavern segments. Our approach, based on the concept of biomass perception, provides a systematic framework for assessing the impact of landscape design on the overall driving experience in urban tunnel environments. 1. This study examines how landscape designs influence safety and comfort in urban tunnels, revealing that optimal solutions require holistic consideration and that patterned designs are best suited for tunnel walls and ceilings, not for road surfaces. 2. This study employs simulated driving and K-means semi-supervised clustering to assess how variations in urban tunnel landscape elements impact driving, using driver biomass as a holistic indicator. The findings indicate that biomass-based assessments can accurately reflect driver states, offering insights into the impact of landscape designs on safety and comfort through machine learning. 3. This study offers valuable theoretical insights for researchers who use biomass to explore the landscape design of urban tunnel cavities, thereby providing a solid foundation for designers involved in tunnel cavity landscape design. Although efforts were made in this paper to quantitatively analyze the design of landscape elements in urban tunnel cavern segments, there are still some shortcomings:  
Firstly, the limited data collection and sample size pose a challenge. This study only incorporated data from a relatively small sample of 30 subject drivers. Considering the individual differences and diverse preferences among the drivers, the small sample size may have hindered the generalizability and reliability of the results. To obtain more accurate assessments of the impact of landscape element design on urban tunnel cavern segments, it is necessary to expand the sample size. Secondly, the study has limitations in terms of considerations. While focusing on factors like biomass perception and driver safety and comfort, other variables, such as traffic flow and road conditions, also influence the design of landscape elements in urban tunnel cavern segments. Failing to adequately address these factors may restrict a comprehensive evaluation of landscape element design in such settings. Furthermore, the generalizability of the proposed evaluation method system based on biomass perception needs further verification. Drivers' perceptions and evaluations of landscape elements may differ across regions and cultural contexts. Hence, it is crucial to conduct cross-regional and cross-cultural studies to validate the applicability of this method in varying contexts. For future research, we can consider recruiting more participants and ensuring that they have diversity in gender, height, age, fatigue level, and driving experience. This will provide a more comprehensive understanding of the differences in tunnel driving safety and comfort among different groups of people. In addition, we can consider introducing other factors, such as tunnel type, width, roof height, vehicle type, etc., to further study the impact of these factors on tunnel driving. Conceptualization, B.L. ; Methodology, Z.L. ; Software, J.X. ; Validation, M.X. ; Formal analysis, J.X. ; Investigation, Z.L. ; Resources, B.L. ; Data curation, H.L. ; Writing--original draft, Z.L. ; Writing--review & editing, Z.L. ; Visualization, M.X. ; Supervision, B.L. ; Project administration, Z.L. All authors have read and agreed to the published version of the manuscript. This research was funded by [National Natural Science Foundation of China] grant number [51878107], [National Natural Science Foundation of China] grant number [51678096], [Project of Chongqing Talent Team] grant number [2019-9-95].