## 2 Materials and Methods
### Concept Definition and Simulation
Following the definition of a single module, it is necessary to define a road train formed by two and four vehicles, which are used in the simulation for different sectors of the route. Also, the definition of a full-size bus is considered to be close to a road train of four autonomous modules. A four-module road train has a maximum passenger capacity of forty-eight people, while the electric bus has a maximum carrying capacity of sixty individuals. Table 3 shows the configuration of two and four connected modules. \begin{table}
\begin{tabular}{c c} \hline \hline
**Specification Type** & **Value** \\ \hline Length & 12,000 mm \\ Width & 2550 mm \\ Height & 3300 mm \\ Weight & 13,790 kg \\ Maximum authorized weight & 18,000 kg \\ Frontal area & 1.97 m\({}^{2}\) \\ Number of seats & 26 \\ Passenger capacity & 60 \\ Drive axle & 2 \(\times\) ZF AVE 130 \\ Maximum motor power & 2 \(\times\) 160 kW \\ Maximum torque & 1450 Nm \\ Battery type & Li-Ion \\ Battery power & 350 kW \\ Battery capacity & 210 kWh \\ Battery voltage & 687 V \\ Suspension type & ZF independent suspension \\ Suspension system & ECAS air suspension with leveling and kneeling functions \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical characteristics of the Solaris Urbino 12 Electric [29; 30]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Reference Item** & **Setting** \\ \cline{2-3}  & **Value** \\ \hline Length & 4000 mm \\ Width & 2000 mm \\ Height & 2750 mm \\ Weight & 2130 kg \\ Maximum motor power & 16 kW \\ Maximum torque & 41.25 Nm \\ Battery capacity & 10 kWh \\ Idle voltage & 48 V \\ Load (front/center/rear) & 300/300/300 kg \\ \hline \hline \end{tabular}
\end{table} 
Table 2: One module configuration. Having defined all the necessary models, the next step in the analysis is to determine the simulation scenarios to be run and routes to be referenced. In order to keep the analysis at a conceptual level, generic cases of public transport routes are taken, as follows:  
* Airport \(\rightarrow\) City Center (AC);
* City Center \(\rightarrow\) Neighborhood (CN);
* City Center \(\rightarrow\) Central Train Station (CT). Route characteristics are taken from Google Maps, using the city of Cluj-Napoca as a source. The routes used indicate all distances, turns, and elevations, combining all kinds of commonly encountered road elements such as climbs, descents, straights, and tight turns. Existing bus routes from Cluj-Napoca that mirror the above-mentioned trajectories are:  
* AC--Cluj \"Avram Iancu\" International Airport (most Eastern part of the city) \(\rightarrow\) Cluj-Napoca City Center;
* CN--Cluj-Napoca City Center \(\rightarrow\) Manastur neighborhood (most Western part of the city);
* CT--Cluj-Napoca City Center \(\rightarrow\) Cluj-Napoca Central Train Station. Figure 3 illustrates the satellite view of the route from the airport to the city center. By extracting the data from the defined route on the map, the CarMaker tool allows users to create a replica of that exact route in the simulation software, taking into account all the elevations, turns, driving lanes, etc. \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Setting**} \\ \cline{2-3}
**Reference Item** & **2 Modules** & **4 Modules** \\ \hline Body Mass & 4260 [kg] & 8520 [kg] \\ Mechanical Power & 32 [kW] & 64 [kW] \\ Max. Torque & 82.5 [Nm] & 165 [Nm] \\ Battery capacity & 416.66 [Ah] & 833.33 [Ah] \\ Idle Voltage & 48 [V] & 48 [V] \\ Load (front/center/rear) & 600/600/600 [kg] & 1200/1200/1200 [kg] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Two and four module configurations. Figure 2: Vehicle outer shell representation in IPG CarMaker. For the purposes of this paper, the simulation is kept simple, without stops, traffic lights, or roundabouts; the route has on its entire length two lanes, one for each travel direction; and the maneuvering of the vehicle is performed following standard driver behavior without exceeding a traveling speed of 20 km/h.