# Walking Speed in a Motorbike Lane Considering the Density of Evacuees and Motorbikes
## 2 Experimental Analysis of Evacuation in the Assumed Motorbike Lane
### Experimental Conditions and Process  
We considered the underground walkway as having two motorbike lanes with a width of 2.6 m and a length of 50 m. Each lane was divided into three sections (see Figure 4). To ensure a stable walking speed of subjects bypassing the area with motorbikes, we set up non-motorbike sections in front and behind the motorbike section to avoid subjects suddenly moving and stopping.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline  & **Assumed Motorbike Lane (Underground Walkway)** & **Real Motorbike Lane (in Cross-Harbor Tunnel)** \\ \hline \multirow{4}{*}{Evacuation scenario} & \(\blacksquare\) & Evacuation only occurs using the lane in the experiment. Subjects only bypass stationary motorbikes, resulting in less risk of collision or injury. & \(\blacksquare\) & Evacuation only occurs using the motorbike lane (no car lanes can be used). Evacuees might encounter moving motorbikes, increasing the risk of collision or injury. \\ \hline \multirow{2}{*}{Evacuation direction} & \multirow{2}{*}{Instructed to be in only one direction.} & Without instruction, evacuation in both directions is possible. \\ \hline \multicolumn{2}{p{113.8 pt}}{Evacuee density} & Controlled by experiment setup. & Variable (depending on situation). \\ \hline \multicolumn{2}{p{113.8 pt}}{Motorbike density} & Controlled by experiment setup. & Variable (depending on situation). \\ \hline \hline \end{tabular}
\end{table}
Table 3: _Cont._  
Figure 3: Evacuation experiment place.  
As demonstrated in Figure 4, subjects wore numbered vests and were asked to orderly start walking (according to the vest number) from the start line to the finish line (\(\text{CP}_{1}\) to \(\text{CP}_{4}\)) to complete the experimental evaluation. Then, subjects were requested to return in the opposite direction according to the staff's instructions to evaluate evacuation from \(\text{CP}_{5}\) to \(\text{CP}_{8}\) as a supplementary experimental evaluation (see Figure 4).  
Typically, users involved in tunnel fire incidents decide to begin evacuating when they (1) see smoke along the ceiling or around them, (2) see other people evacuating, or (3) hear an emergency announcement [8]. In the present study, we focused on clarifying the normal walking speed to investigate the basic evacuation performance characteristics in an emergency such as a fire rather than the maximum evacuation speed considering an extremely urgent condition (i.e., where people may be jogging or semi-jogging). To reproduce the evacuation situation with a purposeful movement characteristic, participants were instructed to walk according to the following oral explanation: \"Please walk through the tunnel as you would normally walk, e.g., as if going to work\" (with the aim of reproducing a situation where subjects walked with a clear destination and not aimlessly).  
Walking speeds were calculated on the basis of the time passed between checkpoints. Checkpoints (CPs) were set using triangular cones and masking tape on the floor. Subjects measured the time passed themselves by pushing the lap time buttons of the stopwatches they carried. To address any issues with the data not being successfully recorded due to the stopwatch button not being pushed, eight video cameras were also placed to record the evacuation process. In addition, the present experiments did not consider hazards such as fire and smoke to ensure the safety of the subjects. Furthermore, the experiments were also aimed at clarifying an evacuation situation where the smoke layer has not yet descended to obscure the evacuation path.  
To investigate the characteristics of the walking speed of motorbike users in the tunnel, we considered two factors that might influence the walking speed of subjects: motorbike density and evacuee density. A detailed consideration regarding these two factors is described in the next two sections.  
Figure 4: Schematic of motorbike lane experiments.