# An Augmented Warning System for Pedestrians: User Interface Design and Algorithm Development
## 4 Discussion  
The purpose of this study was to design an AR-based system to carry visual warning information to pedestrians who are walking in a public area. The interface and the projection algorithm developed in this study show the possibility of providing real-time visual-based warning information to pedestrians using wearable devices. The warning information carried through the interface includes vehicle position, vehicle path, conflict point, collision time, and sidebar. Different pedestrian-vehicle interaction scenarios were studied, and corresponding algorithms were developed. Overall, the developed interface and algorithms presented a reasonable performance that could be used to carry out timely warning information to the pedestrians. The interface was easy to understand for the majority of the participants with minimal learning requirements. All the participants were able to give correct reactions after seeing the warning information. In addition to the interface, the projection algorithm could project \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Time**} & **Distance from Projected** & \multicolumn{2}{c}{**Distance from Projected**} & \multirow{2}{*}{**Average Distance**} \\  & **Vehicle Points to the Ideal** & **Conflict Points to the Ideal** & **Conflict Points to the Ideal** & **Average Distance** \\  & **Path** & **Path** & \\ \hline
1 s & 0.526 & 0.504 & 0.515 \\
2 s & 0.418 & 0.315 & 0.367 \\
3 s & 0.086 & 0.065 & 0.076 \\
4 s & 0.142 & 0.188 & 0.165 \\
5 s & 0.174 & 0.223 & 0.199 \\
6 s & 0.227 & 0.292 & 0.259 \\
7 s & 0.176 & 0.298 & 0.237 \\
8 s & 0.088 & 0.333 & 0.210 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Distance between projected points and ideal points. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time** & **Projected Slope** & **Ideal Slope** & **Difference** \\ \hline
1 s & \(-\)0.071 & \(-\)0.052 & 0.019 \\
2 s & \(-\)0.182 & \(-\)0.130 & 0.052 \\
3 s & \(-\)0.260 & \(-\)0.251 & 0.009 \\
4 s & \(-\)0.286 & \(-\)0.251 & 0.035 \\
5 s & \(-\)0.291 & \(-\)0.251 & 0.040 \\
6 s & \(-\)0.304 & \(-\)0.240 & 0.065 \\
7 s & \(-\)0.322 & \(-\)0.167 & 0.154 \\
8 s & \(-\)0.465 & \(-\)0.251 & 0.214 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Differences between projected and ideal slopes. the vehicle path and show the warning information correctly in real time. As shown in Figure 11, only the first projected vehicle path from the beginning of the data collection was away from the ideal path; all other projected paths were closer to the ideal path and provided the correct vehicle information to the pedestrians. Although the first projected vehicle path was away from the ideal path, the slope of the projected path matched the ideal path, which meant, even though the projected path was not overlaid on the correct lane of the road, the vehicle direction was still projected correctly. The slopes between the projected path and the ideal path were compared, and the average difference was only 0.074, which was small enough to give the pedestrian correct information. Among all the data, the lowest difference between the ideal slope and the projected slope was 0.009, and the largest difference was 0.214. On average, the closer the vehicle was to the pedestrian, the higher was the observed difference in slope. When the vehicle was getting closer to the pedestrian, the distance between vehicle point and conflict point was shorter, and the slope difference got larger, even with a small mismatch between projected points and ideal points. It was acceptable when the slope difference was getting larger when the vehicle was getting closer to the pedestrians, since pedestrians could more easily identify the vehicle and the vehicle path regardless of the potential projection errors, as the vehicle was near the conflict point. The distances between the projected path and the ideal vehicle path were also compared. The average distance between projected points to the ideal vehicle path was 0.253.