# Assessing Traffic-Flow Safety at Various Levels of Autonomous-Vehicle Market Penetration
## 4 Results
### Design of Exclusive Lane for AVs  
An analysis of mixed traffic safety on a 640 m stretch of the I-101 highway in the United States found that, as the adoption rate of autonomous vehicles increases, through traffic increases and the number of conflicts decreases. However, when analyzing conflicts between conventional vehicles and autonomous vehicles, the number of conflicts increases as the adoption rate increases until the adoption rate of autonomous vehicles reaches 30%. When the adoption rate of autonomous vehicles is 20%, it is necessary to reduce the risk of rear-end collisions between conventional vehicles and autonomous vehicles and side collisions when the leading vehicle is an autonomous vehicle and the trailing vehicle is a conventional vehicle. When the adoption rate of autonomous vehicles is 30%, it is necessary to reduce the risk of side collisions when the leading vehicle is a conventional vehicle and the trailing vehicle is an autonomous vehicle. Therefore, until the adoption rate of autonomous vehicles reaches 30%, it was determined that it is necessary to operate an autonomous vehicle lane that separates conventional vehicles from autonomous vehicles in order to minimize conflicts between conventional vehicles and autonomous vehicles. As presented in Table 9, based on the results of the operational efficiency analysis, we calculated the traffic volume of autonomous vehicles according to the adoption rate of autonomous vehicles using the passing traffic volume and, then, calculated the traffic volume according to the number of lanes in the autonomous-vehicle lane. The number of lanes for autonomous-vehicle lanes was also examined until the ratio of traffic per lane for general vehicles and autonomous-vehicle lanes was 1:1. Finally, the operational options to be considered when establishing the operational plan for the autonomous-vehicle lane for the spatial scope of this study are illustrated in Figure 4. These options include one and two lanes, if the autonomous vehicle lane is on the left, and one and two lanes if the autonomous vehicle lane is on the right. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multicolumn{4}{c}{**Side Collision**} & \multicolumn{4}{c}{**Rear Collision**} & \multicolumn{4}{c}{**Total**} \\ \cline{2-13}  & **TTC 1** & **TTC 2** & **TTC 3** & **TTC4** & **TTC 1** & **TTC 2** & **TTC 3** & **TTC4** & **TTC 1** & **TTC 2** & **TTC 3** & **TTC4** \\ \hline \hline MPR 10\% & 19.8 & 7.0 & 11.0 & 6.6 & 4.4 & 0.0 & 0.0 & 0.2 & 24.2 & 7.0 & 11.0 & 6.8 \\ MPR 20\% & 29.0 & 10.0 & 10.8 & 6.2 & 66.8 & 9.0 & 17.4 & 36.0 & 95.8 & 19.0 & 28.2 & 42.2 \\ MPR 30\% & 89.6 & 26.4 & 38.2 & 27.2 & 17.4 & 0.2 & 1.0 & 0.4 & 107.0 & 26.6 & 39.2 & 27.6 \\ MPR 40\% & 30.2 & 6.2 & 8.8 & 4.6 & 20.8 & 0.6 & 0.2 & 0.2 & 51.0 & 6.8 & 9.0 & 4.8 \\ MPR 50\% & 19.4 & 5.0 & 4.8 & 3.8 & 23.4 & 0.6 & 0.2 & 0.4 & 42.8 & 5.6 & 5.0 & 4.2 \\ MPR 60\% & 6.8 & 1.4 & 1.8 & 1.8 & 24.4 & 1.2 & 0.6 & 1.0 & 31.2 & 2.6 & 2.4 & 2.8 \\ MPR 70\% & 5.0 & 1.4 & 0.8 & 0.2 & 20.4 & 0.6 & 0.8 & 0.4 & 25.4 & 2.0 & 1.6 & 0.6 \\ MPR 80\% & 2.6 & 0.0 & 1.0 & 0.0 & 17.0 & 0.0 & 0.0 & 0.4 & 19.6 & 0.0 & 1.0 & 0.4 \\ MPR 90\% & 0.6 & 0.4 & 0.2 & 0.0 & 10.0 & 0.0 & 0.0 & 0.4 & 10.6 & 0.4 & 0.2 & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Conflict risk analysis results by case (HDV-AV) (unit: times). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{**Mixed-Flow**} & \multicolumn{2}{c}{**Operate 1 Exclusive Lane**} & \multicolumn{2}{c}{**Operate 2 Exclusive Lanes**} \\  & & **for AV** & & **for AV** \\ \cline{2-5}  & & **HDV Lane** & **Ex. Lane for AV** & **HDV Lane** & **Ex. Lane for AV** \\ \hline MPR 10\% & 929 & 1045 & 464 & 1393 & 232 \\ MPR 20\% & 992 & 992 & 992 & 1322 & 496 \\ MPR 30\% & 1061 & 928 & 1592 & 1238 & 796 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Design exclusive lanes for AVs (unit: veh/lane).