## 3 Results
### Quantitative Evaluation (Experimental Results)
Yet, that difference is much smaller for the LC and SCmodes. It is also evident that the portion of time driving with a low TLC increases abruptly during the distraction event for MANUAL and LK modes, but does not increase much for LC and SC modes. Furthermore, for both conditions, the SC mode leads to the highest RMS TLC, with similar MIN TLC excursions to those of the LC mode. A further suggestion of the effect of the curvature anticipating feedback from the LK is depicted by the time spent below the TLC threshold in normal driving. Overall, concerning the safety indicators, SC is the one that moves further away from the drawbacks of MANUAL, and gets closer to the lower TLC of Automation-only, under both normal driving and distraction events. Thus, this highlights the benefits of the \"team\" approach. The driving efforts (Figures 13 and 14) provide insight into the driver/automation interaction or conflict. The driver torque is, of course, zero for Automation-only, whereas automation torque is zero for MANUAL driving mode. Then, for both conditions (normal driving and during distraction), the RMS torque of the automated modes is smallest for LC and largest for LC. When the automation is present, the driver torque shows a similar trend to that of the automation, but it must be noted that this similarity is not direct. At points, the automation torque \"helps\" the driver, pushing in the same direction, while at other times the automation \"corrects\" the driver with an opposing torque. Taking the driver torque on manual mode as the reference, the driver effort is reduced by the LK, particularly during the distraction event, notoriously because the major corrections required by the largest excursions when approaching lane borders are supported by the LK strategy. The LC mode, on the other hand, increases driver effort in normal driving, since the conflict when wandering around the centerline produces an automation correction torque. During the distraction event, the LC shows an RMS driver torque similar to that of the MANUAL mode, in this case, to resist the automation guiding torque, which reduces the MAX efforts by bounding the off-center excursions (see Figure 9). The SC mode reduces both the RMS torque and the occasional large excursion corrections in normal driving by reducing the guiding conflict (with a lower authority) and bounding the off-center excursions before approaching the lane limits. Finally, during the distraction event, the SC mode reduces the tracking errors by applying a larger authority as discussed above. These smaller tracking errors also translate into reduced driver efforts compared to LC and MANUAL modes. To summarize, when attentive, the driver can keep a very small tracking deviation in all modes (see Figure 9). In those cases, the SC mode provides very little support, and the driver feels very close to manually driving, being free to wander within a narrow band around the center. Only when the occasional larger deviation occurs, the SC provides centering feedback. On the other hand, even when the tracking errors are small, the LK will provide feedback indications when the steering is heading towards a possible lane crossing (i.e., when the TLC is small). The LC will always provide feedback even with small tracking errors. Thus, considering tracking performance, LC and SC modes seem to provide the best results. When looking at the safety indicators, SC shows the highest performance, closely followed by the LC mode. Yet, in terms of effort, the lowest driver effort is required by the LK mode, followed by the SC, while the LC presents the highest driver torque conflict. Overall, considering tracking, safety, and effort parameters, SC mode seems to give the best compromise amongst the tested modes, being the farthest of all from MANUAL, and the closest to Automation-only, thus, encouraging the idea of being a \"team\". Moreover, it seems worth evaluating a mode combining the benefits of SC with the curve-anticipating torque of the LK mode.