## 5 Field Test Configuration and Results
### Credibility Evaluation Results
#### 5.2.2 Results of Scenario-Based Evaluation
Specifically, the inter-repetition consistency index for the real-vehicle tests decreased from 0.922 under the low-speed condition to 0.873 under the high-speed condition in Scenario A, and from 0.846 to 0.806 in Scenario F. This reflects the physical phenomenon in which maintaining consistency in vehicle behavior becomes more difficult as speed increases, because factors such as inertial forces, tire dynamics, and steering sensitivity interact more complexly, resulting in greater variability in system responses to the same inputs. Additionally, the consistency indices for Scenarios C and D were lower than those for Scenarios A and B; this shows that the inclusion of the target vehicle increased the structural complexity of the scenarios, whereby ensuring consistency in system responses between repeated experiments became more difficult. The consistency index between the real-vehicle and VILS tests was also significantly lower in the integrated behavior scenarios (E and F) than in the single-behavior scenarios (A-D). Particularly under the high-speed condition, Scenarios E and F recorded the lowest values, at 0.681 and 0.676, respectively. This reflects the increasing difficulty in ensuring coherent multi-dimensional system responses due to the inclusion of both longitudinal and lateral terms in the main parameters used for the consistency index calculations. Table 5 presents the correlation index and applicability index for each scenario as percentages, with all metrics meeting the pre-established criteria across all scenarios. Notably, the applicability index exceeded 100% in all scenarios and under all speed conditions. This numerically verifies that the VILS tests were more repeatable and reproducible than the real-vehicle tests, indicating that the VILS environment was sufficiently reliable to replace real-vehicle testing. Under the high-speed condition in Scenario D, the applicability index recorded its highest value (110.37%), which suggests that VILS tests can provide more consistent results than real-vehicle tests even in complex and challenging driving situations. The correlation index also exhibited a consistent pattern with respect to the speed condition, displaying a decreasing trend with increasing speed across all scenarios. In Scenario A, the correlation index decreased from 95.79% under the low-speed condition to 92.49% under the high-speed condition, while in Scenario E, it underwent a larger reduction, from 89.53% to 82.81%. This observation can be interpreted as the dynamic differences between real and simulated vehicles becoming more pronounced in higher-speed driving situations. Interestingly, the single-behavior scenarios (A-D) showed higher correlation indices than the integrated-behavior scenarios (E and F), which suggests that VILS environments can be more coherent in relatively simple scenarios. Conversely, the applicability index tended to be higher in more complex scenarios and under higher-speed conditions. Under the high-speed condition in Scenario D, it recorded its highest value (110.37%), which signifies that the VILS tests were more consistent than the real-vehicle tests under more complex conditions.