# Steady-Speed Traffic Capacity Analysis for Autonomous and Human-Driven Vehicles
## 4 Results
### Space Headway, Time Headway, Density, and Capacity Analysis
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Speed** & **Parameter** & **Human-Driven** & **Subaru** & **Volvo** & **VW** & **Subaru/Human \% Decrease** & **VW/Human** \% Decrease** & **VW/Human**\% Decrease** \\ \hline
30 & Density & 84 & 66 & 81 & 60 & 21.4 & 3.5 & 28.2 \\  & [veh/km] & Capacity & 2505 & 1970 & 2417 & 1799 & 21.4 & 3.5 & 28.2 \\  & [veh/h] & Density & 70 & 61 & 60 & 53 & 12.9 & 13.5 & 24.1 \\
40 & [veh/km] & Capacity & 2796 & 2436 & 2417 & 2121 & 12.9 & 13.5 & 24.1 \\  & [ven/h] & Density & 59 & 54 & 54 & 47 & 9.7 & 8.8 & 20.4 \\
50 & [veh/km] & Capacity & 2962 & 2675 & 2703 & 2356 & 9.7 & 8.8 & 20.4 \\  & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average traffic densities and capacities obtained by using test vehicles. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Speed [km/h]** & **Parameter** & **Human-Driven** & **Subaru** & **Volvo** & **VW** \\ \hline
30 & Space [m] & 11.976 & 15.227 & 12.410 & 16.680 \\  & Time [s] & 1.437 & 1.827 & 1.489 & 2.002 \\
40 & Space [m] & 14.308 & 16.422 & 16.549 & 18.856 \\  & Time [s] & 1.288 & 1.478 & 1.4  
Figures 15 and 16 summarize the results of the entire study, encompassing all analyzed measurements to facilitate a comprehensive comparison of relevant parameters. Figure 15 illustrates the relationship between clearance and density, demonstrating a smooth decrease in density with the gradual increase in clearances resulting from the incremental rise in speed for all tested vehicles. Conversely, Figure 16 depicts the impact of increasing clearances on capacity, indicating the time headway by the size of the dots in the graph. The graph portrays an almost seamless increase in capacity with respect to the growing speed and subsequently increased clearances for both human-driven and VW vehicles. Subaru follows a similarly smooth trend in the graph, except at 90 km/h, where a sharp drop occurs. This can be attributed to the relatively high difference in time headway, when 1.136 s and 1.207 s were reported at driving speeds of 80 km/h and 90 km/h, respectively. In contrast, Volvo yielded more oscillated capacity results due to its reliance on time settings of ACC rather than distance settings as for Subaru and VW. At the end of our analysis, Figure 17 provides a comprehensive depiction of the intricate relationship between capacity and density across all driving modes, examined under driving speeds. This visual representation serves to underscore and elucidate the assertions made earlier in our investigation, specifically focusing on the performance of vehicles with respect to car-following behavior. As discerned from the data presented in Figure 17, both human-driven vehicles and VW demonstrated notably superior \(R^{2}\) values, attaining 0.94 and 0.97, respectively. In stark contrast, Subaru and Volvo vehicles exhibited lower \(R^{2}\) values of 0.85 and 0.82, respectively. This discrepancy in \(R^{2}\) values underscores the distinctive car-following behaviors exhibited by these vehicle types under the conditions of our study, with human-driven and VW vehicles outperforming their Subaru and Volvo counterparts. Such insights contribute to an understanding of the dynamics associated with different driving modes and vehicles in the context of field driving speeds and car-following behavior.