## 4 Results and Discussion  
### Speed Analysis  
Vehicles' mean spot speeds at entry, exit, and average speeds within the examined tunnel sections were collected and analysed to study driving behaviours. A significant amount of data was obtained from the three different scenarios. The measured standard deviation, mean, minimum, and maximum values of vehicle speeds (km/h) for entry, exit, and average speeds, as well as the speed change rates (see Equation (1)), were determined for each of the three tunnel lighting scenarios across all drivers. These results are summarized in Table 2.  
\[SR_{S_{ij}}=\frac{SE_{sij}}{SI_{sij}} \tag{1}\]  
where:  
\(SR_{sij}\) Speed reduction ratio for scenario \(i\) and lighting colour \(j\). \(SE_{sij}\) Speed for the entrance of scenario \(i\) and lighting colour \(j\) (km/h). \(SI_{sij}\) Speed for the inside the examined tunnel sections of scenario \(i\) and lighting colour \(j\) (km/h). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Scenario-No**} & **Tunnel Lighting** & **Lighting Length** & **Langle Number** & **Langle Width** & **Lateral Clearance** & **Sidewalk Width (Left + Right)** & **Obstacle in the Red** \\  & **Colour** & **(m)** & **(m)** & **(m)** & **(Left + Right)** & **Right)** & **Tunnel Light** \\ \hline S-1 & Blue Sky & 210 & 2 & 3.50 + 3.50 & 0.50 + 0.50 & 1.00 + 1.00 & - \\ \hline \multirow{2}{*}{S-2} & Red & 210 & 2 & 3.50 + 3.50 & 0.50 + 0.50 & 1.00 + 1.00 & 100 \\ \cline{2-8}  & Green & 210 & 2 & 3.50 + 3.50 & 0.50 + 0.50 & 1.00 + 1.00 & - \\ \hline \multirow{4}{*}{S-3} & Flashing Red & \multirow{2}{*}{210} & \multirow{2}{*}{2} & \multirow{2}{*}{3.50 + 3.50} & \multirow{2}{*}{0.50 + 0.50} & \multirow{2}{*}{1.00 + 1.00} & - \\  & on Tunnel Wall & & & & & & \\ \cline{1-1} \cline{2-8}  & Red & 210 & 2 & 3.50 + 3.50 & 0.50 + 0.50 & 1.00 + 1.00 & 60 \\ \cline{1-1} \cline{2-8}  & Green & 210 & 2 & 3.50 + 3.50 & 0.50 + 0.50 & 1.00 + 1.00 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Geometric properties of the tested scenarios. According to Table 2, vehicle speeds decreased in tunnel sections with red tunnel lights and flashing lights on the tunnel walls. It was concluded that drivers felt uncomfortable and reduced their speed due to the red lighting, which signalled a dangerous situation in these sections. Similarly, it was observed that drivers increased their speed in areas with green overhead lights, indicating that they had passed the dangerous section and could safely continue their journey. In S-1, drivers did not significantly increase their speed in the sections with blue sky lighting, which was designed to reduce stress in areas where drivers typically feel overwhelmed. This suggests that the blue lighting has a more significant effect on drivers' psychological relaxation rather than on their speed. The S-1 is already implemented in many tunnels worldwide, and the results from the simulator are consistent with real-world findings. In contrast, when analysing S-2 and S-3, which were specifically designed for this study, it was found that S-3 was more effective at reducing drivers' speed as they approached the dangerous tunnel section. As expected, the results confirm that the tunnel lighting scenarios (S-2 and S-3) have a positive impact on speed reduction in response to perceived danger. The results in Table 2 and Figure 7 indicate that drivers tend to maintain higher speeds in tunnels when road comfort and traffic flow are optimal. However, a significant reduction in driver speed was observed in sections where newly added red tunnel light warnings were present, compared to other road sections. An ANOVA test was conducted to examine the effect of three different tunnel safety scenarios on mean spot speeds. The mean of spot speed data 'before' and 'inside' the scenarios for all 125 drivers were first tested for normality and homogeneity of variance prior to performing the ANOVA test. Bartlett's Test was used to assess the homogeneity of variance (Table 3).