## 4 Experimental Design and Results
### Ablation Experiment
Their contribution varies across different driving scenarios. During high-speed driving, drivers are in a highly tense state, and changes in the respiratory rate can reflect the driver's physiological responses. Experimental results show that after removing the respiratory rate signal, the system's accuracy decreased by 5.58%, indicating that respiratory rate signals effectively supplement heart rate signal information and play a crucial auxiliary role in fatigue and stress monitoring. The contribution of respiratory rate signals is significant in rapid driving scenarios, especially when drivers need to frequently adjust their driving behavior, as the respiratory rate can reflect subtle changes in fatigue or stress levels. The system's accuracy decreased by 7.44% after removing the respiratory rate signal, suggesting that this signal is an important indicator in rapid driving conditions. In low-speed driving, the physiological fluctuations of drivers are smaller, but the respiratory rate can still provide some monitoring information. After removing the respiratory rate signal, the system's accuracy decreased by 5.48%, indicating that while the signal's contribution is relatively limited in low-speed driving, it still holds some auxiliary value. In traffic congestion, the driver's respiratory rate typically increases with rising stress levels. Experiments show that after removing the respiratory rate signal, the system's accuracy decreased by 6.96%, highlighting the importance of respiratory rate signals in monitoring driver stress responses during congestion. Respiratory rate signals demonstrate the most significant contributions in rapid driving \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Configuration** & **Precision** & **Accuracy** & **Recall** & **F1 Score** & **False Positive Rate** \\ \hline Complete multimodal fusion & 84.55\% & 85.18\% & 85.12\% & 84.88\% & 8.42\% \\ \hline Removal of heart rate signal & 72.53\% & 74.13\% & 75.96\% & 74.58\% & 10.81\% \\ \hline Removal of respiratory rate signal & 76.59\% & 78.22\% & 78.26\% & 77.54\% & 10.75\% \\ \hline Removal of skin conductance signal & 81.16\% & 82.57\% & 81.27\% & 81.88\% & 9.96\% \\ \hline Removal of body pressure & & & & & \\ distribution signal & 80.27\% & 80.37\% & 80.95\% & 80.11\% & 9.89\% \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Results of ablation experiments under traffic congestion conditions. and congested conditions, effectively supplementing heart rate signals, particularly in the sensitive monitoring of fatigue and stress levels. Skin conductance signals primarily monitor the driver's emotional fluctuations and stress responses, with their role being relatively limited in certain driving scenarios. However, in high-stress situations, they can provide critical supplementary information. Due to the high attention demands of high-speed driving, skin conductance signals can reflect the driver's emotional fluctuations during sudden situations or increased pressure. After removing skin conductance signals, the system's accuracy decreased by 5.82%, indicating a moderate contribution of this signal in high-speed driving. In rapid driving, the role of skin conductance signals is minimal, with the accuracy decreasing by only 3.23% after removing this signal. This indicates that in scenarios with relatively lower pressure, the contribution of skin conductance signals is low. During low-speed driving, the driver's stress is typically lower, and fluctuations in skin conductance signals are minimal. After removing this signal, the system's accuracy decreased by 3.22%, indicating a weak influence on the system. In congested conditions, skin conductance signals can effectively reflect the driver's tension and stress responses. Experiments show that the system's accuracy decreased by 2.61% after removing skin conductance signals, indicating a certain contribution to stress state monitoring in congestion scenarios.