## 4 Evaluation of Automatic Idling Control of CAVs
### Results and Analysis  
This study evaluated the temporal and environmental benefits of autonomous vehicles under C-ITS when automatically controlling idling in the case that the informed waiting time is longer than the reference time in the Haeundae-gu network.  
Table 3 shows that the total number of vehicles analyzed in this study is 15,888 vehicles, and 99.5% of them (i.e., 15,813 vehicles) were forced to experience idling at least once until leaving the network, resulting in 1602 idling hours out of total travel time, 3173 h, which is approximately 50.5%. The average travel time per vehicle is 719 s/veh, which is the sum of average moving time (354 s/veh) and average idling time (365 s/veh). The total saved idling time by applying the automatic vehicle idling control function proposed in this study is 1511 h, which accounts for 47.6% of the total travel time and 94.3% of the total idling time, respectively. The average saved idling time is 334 s/veh, which is the same percentage as the saved travel time.  
Table 3 also reveals that the total CO\({}_{2}\) emissions from all vehicles is 64,641,228 kg/h at an average of 4069 kg/h. The amount of CO\({}_{2}\) emissions from idling vehicles takes up 25.0% of the total CO\({}_{2}\) emissions, which is 1017 kg/h per vehicle on average. The saved CO\({}_{2}\) emissions due to the proposed function in this study corresponds to 23.6% of the total CO\({}_{2}\) emissions and 94.3% of the total idling CO\({}_{2}\) emissions, respectively. Therefore, the proposed function enables idling time and CO\({}_{2}\) emitted during idling to be significantly reduced by over 94% without relying on human judgement.  
In addition to the total and average travel time and CO\({}_{2}\) emissions in terms of vehicle unit, it is noteworthy to analyze them at the individual idling level. Table 4 shows that the total number of idling experienced by 15,813 vehicles is 113,986 times, which is 7.2 times per vehicle on average. Their average time and emission per idling are 50.6 s and 142 kg/h, respectively. Consequently, approximately 134 kg/h CO\({}_{2}\) emissions out of 142 kg/h, accounting for 94.3% of the total, were saved by the automatic vehicle idling control function,  
\begin{table}
\begin{tabular}{c c} \hline
**Item** & **Value** \\ \hline Rolling resistance (\(A\)) & 0.156461 (kW-s/m) \\ Rotating resistance (\(B\)) & 0.00200193 (kW-\(s^{2}\)/m\({}^{2}\)) \\ Drag resistance (\(C\)) & 0.000492646 (kW-s\({}^{3}\)/m\({}^{3}\)) \\ Source mass (\(m\)) & 1.4788 (ton) \\ Fixed mass factor (\(m_{fixed}\)) & 1.4788 (ton) \\ \hline \end{tabular}
\end{table}
Table 2: MOVES default database in Equation (1).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Time**} & \multicolumn{3}{c}{**Emission**} \\ \hline  & **Total** & **Average** & **Rate** & **Total** & **Average** & **Rate** \\ \hline Vehicles & 3173 h & 719 s/veh & & 64,641,228 kg/h & 4069 kg/h & \\ Idling & 1602 h & 365 s/veh & 50.5\% & 16,152,220 kg/h & 1017 kg/h & 25.0\% \\ Saved & 1511 h & & & 959 kg/h & \\ idling & (94.3\%) & 344 s/veh & 47.6\% & 15,230,566 kg/h & (94.3\%) & 23.6\% \\ \hline \end{tabular}
\end{table}
Table 3: Temporal and environmental effects of automatic vehicle idling control function.  
which was executed based on the queue discharge time, reference time, and traffic signal information transmitted from the traffic signal controller through V2I communication.