## 5 Simulation Results
### Evaluating the Impact of the Roadmap  
This subsection presents the results obtained when varying the roadmap used. We selected scenarios from New York, San Francisco, and Rome. In Table 9 we present the main features of the chosen fragments of the cities.  
Table 4 shows some of the parameters used for the simulations; the rest of parameters are the following: 200 vehicles are simulated, the radio propagation model used is RAV, vehicles follow the Krauss mobility model, there are 3 warning mode vehicles, the periodicity of messages is 1 message per second, normal message priority is AC0, the broadcast scheme applied is eMDR, and the channel bandwidth is 6 Mbps.  
As shown, the warning notification time is lower when simulating the New York map (see Figure 7). Information reaches about 60% of the vehicles in less than \(0.8\) s, and propagation is completed in \(5\) s. When simulating the map of San Francisco, information needs more time (\(1.4\) s) to reach the same  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Selected city map** & **New York (USA)** & **San Francisco (USA)** & **Rome (Italy)** \\ \hline
**Streets/km\({}^{2}\)** & \(175\) & \(428\) & \(695\) \\
**Junctions/km\({}^{2}\)** & \(125\) & \(205\) & \(298\) \\
**Avg. street length** & 122.55 m & 72.71 m & 45.89 m \\
**Avg. lanes/street** & \(1.57\) & \(1.17\) & \(1.06\) \\ \hline \hline \end{tabular}
\end{table}
Table 9: Main features of the selected maps.  
Figure 6: Evolution of the warning message dissemination process in the Rome scenario after 20 s, when simulating (**a**) 100 and (**b**) 400 vehicles.  
percentage of vehicles. As for Rome, the propagation process was completed in only \(2.4\) s, but less than 40% of the vehicles are informed.  
The behavior in terms of percentage of blind vehicles and the number of packets received also highly depends on this factor (see Table 10). In fact, when simulating New York, the percentage of blind vehicles is almost negligible, while we find \(60.92\%\) of blind vehicles when simulating Rome. Hence, when the simulated layout is more complex, the percentage of blind vehicles increases, and more time is needed to reach the same percentage of vehicles. This occurs mainly because the signal propagation is blocked by buildings. Moreover, the average number of packets received per vehicle highly differs depending on the map. Compared with New York, the number of packets received decreases considerably for San Francisco and even more for Rome since signal propagation encounters more restrictions.  
Figure 8 shows the number of warning messages received in each area when simulating New York, San Francisco, and Rome, respectively. As mentioned before, when simulating the New York scenario the dissemination process is able to reach a wider area since streets are longer and wider, and there are fewer junctions, so messages can be disseminated more easily.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Roadmap** & **\% of Blind Vehicles** & **Packets Received** \\ \hline New York & 2.92\% & 1,542.07 \\ San Francisco & 20.55\% & 885.13 \\ Rome & 60.92\% & 229.07 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Blind vehicles and packets received per vehicle when varying the roadmap.  
Figure 7: Warning notification time when varying the roadmap.