## 4 Experimental Evaluation
### Cut-In Driving Scenario
#### 4.3.2 Performance Evaluation  
The ground truth relative position of the remote vehicle and the absolute error for the relative position during the cut-in driving scenario 1 are shown in Figure 13. The longitudinal and lateral relative distance measurements obtained from separate test runs are concatenated and shown together. The start and the duration of the cut-in events can be conveniently observed in Figure 13b, where the lateral distance changes from the center of the adjacent lane towards the center of the lane that the host vehicle is positioned. The TTC results and the corresponding levels of the collision warning obtained from the proposed method for trajectory prediction and risk assessment are presented in Figure 14. Possible collision events are successfully predicted for all four cut-in maneuvers performed by the remote vehicle. The TTC results for the collision detection shown are above 4 s except the third cut-in case. The levels of these threats other than the third one are minor, resulting in level-1 warnings only for a short duration of time. A level-2 warning is given for the third cut-in event, which is due to the more abrupt change in the longitudinal distance just prior to and during the lane-change maneuver. Figure 15 shows the ground truth position and the absolute position error in longitudinal and lateral directions during the cut-in driving scenario 2. The data collected from separate test runs are concatenated as presented. A total of five cut-in events take place in this scenario, and the start and the duration of these events can be observed in Figure 15b. The TTC results and the corresponding collision warning levels are presented in Figure 16. For all five cut-in maneuvers performed by the remote vehicle in the scenario 2, possible collision events are correctly predicted and corresponding collision warnings are provided. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scenario** & **Host Vehicle** & **Remote Vehicle** & **Cut-In** & **Number of Cut-In** \\
**Number** & **Speed (km/h)** & **Speed (km/h)** & **Distance (m)** & **Maneuvers** \\ \hline
1 & 40–45 & 35–40 & 15–20 & 4 \\
2 & 40–45 & 25–30 & 15–20 & 5 \\
3 & 40–45 & 15–20 & 15–20 & 8 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Cut-in driving scenario descriptions. Figure 12: Relative positioning accuracy in the longitudinal and lateral directions for the combined sets of the measurements obtained from the two normal driving scenarios. Figure 13: Relative distance to the remote vehicle during the cut-in driving scenario 1. (**a**) Ground truth longitudinal distance; (**b**) ground truth lateral distance; (**c**) absolute error for longitudinal distance estimates; (**d**) absolute error for lateral distance estimates. Figure 14: Potential crash events predicted during the cut-in driving scenario 1. (**a**) Time-to-collision (TTC); (**b**) collision warning level. Figure 15: _Cont._  
Figure 17 presents the ground truth relative position of the remote vehicle and the absolute error for the relative position during the cut-in driving scenario 3. The data obtained from separate test runs are concatenated and presented together. A total of eight cut-in events can be recognized in Figure 17b. An unusual remote vehicle maneuver in the lateral direction can be noticed before the initiation of the fourth cut-in maneuver. This was caused by an incident where our driver of the remote vehicle steered away to avoid another vehicle that was used by a different group in the proving ground. Despite the higher fluctuations of the position estimates from the individual remote sensing systems as shown in Figure 17c,d, the proposed cooperative approach provides accurate and reliable positioning results throughout the execution of cut-in maneuvers.