Driver Engagement and Fully Shared Longitudinal Control Insights From Real Partially Automated Vehicles

While the capabilities of partially automated Advanced Driver Assistance Systems (ADAS) have increased significantly, keeping the driver engaged in the driving task remains an ongoing challenge. One novel approach are fully shared longitudinal control ADAS, which allow drivers to intervene with braking without deactivating automated assistance, enabling more seamless cooperation. This paper investigates the impact of fully shared longitudinal control on driver engagement in urban environments using real vehicles. Two complementary studies-a real-vehicle trial with 50 experienced drivers and a mixed-reality simulation with 37 participants-were conducted, employing both subjective and objective engagement metrics. Results show that fully shared longitudinal control significantly increases ADAS usage and driver-initiated brake interventions, indicating increased physical engagement. Moreover, participants reported higher levels of acceptance and user experience, while cognitive workload was reduced compared to conventional systems, fostering emotional and potentially cognitive engagement. The findings highlight the benefits of fully shared longitudinal control for enhancing driver engagement and improving humanautomation teamwork, leading to safer, more engaging, and satisfying automated driving.