# Assessing Traffic-Flow Safety at Various Levels of Autonomous-Vehicle Market Penetration
## 4 Results
### Design of Exclusive Lane for AVs
When the number of conflicts was analyzed for the four autonomous-vehicle lane design options, as presented in Table 10, the lowest number of conflicts was found when the autonomous-vehicle lane was installed with two lanes on the left side. In addition, the number of conflicts was lower when the autonomous-vehicle lane was designed on the left side than when it was designed on the right side, and the number of conflicts was higher when the autonomous-vehicle lane was designed on the right side than when the autonomous vehicle lane was designed on the left side. Designing a dedicated lane on the right side of the road resulted in fewer conflicts for one lane of autonomous vehicles than for two lanes of autonomous vehicles until the adoption rate of autonomous vehicles reached 20%. This is likely due to the fact that the on-ramp is located on the right side, which requires more vehicles to change lanes from the main road to the on-ramp or from the on-ramp to the main road compared to a lane dedicated to autonomous vehicles on the left side or a mixed-use road. In addition, when comparing the two right-lane options, the number of HDV-AV conflicts was higher when the adoption rate of autonomous vehicles was 10% than when the right lane was two lanes. This is because when the adoption rate of autonomous vehicles is 20% or higher, the traffic volume per lane is analyzed, and it is relatively difficult for entering and exiting vehicles to change lanes due to the higher traffic volume in the lane dedicated to autonomous vehicles compared to the lane dedicated to regular vehicles, which causes more rear-end conflicts when the trailing vehicle is a regular vehicle. Therefore, in the spatial scope of this study, it is recommended to install two lanes on the left side of the autonomous-vehicle lane until the adoption rate of autonomous vehicles reaches 30%. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Case**} & \multicolumn{3}{c}{**Mixed Flow**} & \multicolumn{3}{c}{**1 Lane (Left)**} & \multicolumn{3}{c}{**2 Lanes (Left)**} & \multicolumn{3}{c}{**1 Lane (Right)**} & \multicolumn{3}{c}{**2 Lanes (Right)**} \\ \cline{2-13}  & **HDV-** & **HDV-** & **Sum** & **HDV-** & **HDV-** & **Sum** & **HDV-** & **HDV-** & **Sum** & **HDV-** & **HDV-** & **Sum** & **HDV-** & **HDV-** & **HDV-** & **Sum** \\  & **HDV** & **AV** & **HDV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** & **AV** \\ \hline \hline MPR 10\% & 169.2 & 49.0 & 218.2 & 153.6 & 4.2 & 157.8 & 133.8 & 3.6 & 137.4 & 132.0 & 83.2 & 215.2 & 265.0 & 75.4 & 340.4 \\ MPR 20\% & 679.3 & 185.2 & 864.6 & 141.0 & 21.8 & 162.8 & 117.4 & 9.2 & 126.6 & 120.2 & 194.8 & 315.0 & 203.0 & 118.4 & 321.4 \\ MPR 30\% & 138.6 & 200.4 & 339.0 & 126.0 & 44.2 & 170.2 & 100.0 & 17.4 & 117.4 & 107.2 & 268.0 & 375.2 & 115.2 & 136.6 & 251.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Safety assessment results by exclusive AV lane operation plan (unit: times). Figure 4: Design of exclusive lane for AVs. To analyze the traffic aspect, we analyzed the average traffic speed of the main road for each autonomous-vehicle lane operation plan, as presented in Table 11. We found that the average traffic speed is similar at about 40.43 km/h regardless of the autonomous-vehicle lane operation plan. This indicates that the lane change of entering and exiting vehicles does not have a significant impact on traffic. Dedicated lanes for autonomous vehicles have the potential to enhance road safety while maintaining average travel speeds comparable to those on mixed-flow roads. Consequently, until the adoption rate of autonomous vehicles reaches 30%, and there exists a high risk of conflict between AVs and regular vehicles, implementing dedicated autonomous-vehicle lanes emerges as a favorable road management strategy.