Semi-Automated Driving Has Higher Workload and Is Less Acceptable to Drivers than Manual Vehicles

Abstract

SAE Level 2 semi-autonomous vehicles (AVs) are in active use on the road, and SAE Level 3 AVs will be with us soon. Although the vehicles provide support for longitudinal and lateral control, semi-automated driving experience is sometimes more demanding or less satisfying than manual driving. However, the effects of autonomous driving on workload and acceptance in naturalistic conditions have not been extensively investigated as most studies have been undertaken in driving simulators. This study extends our understanding about workload and acceptance in SAE Level 2 AVs on public roads. Drivers’ perceived workload and acceptance were assessed after conducting manual and automated driving in three Level 2 AVs, in highway and urban environments. The comparative findings revealed that drivers’ workload was higher, and acceptance was lower, in semi-automated driving when compared to manual driving. Furthermore, workload was higher, and acceptance was lower, in urban than in highway driving. The findings provide insights for stakeholders to better understand the experience of current SAE Level 2 autonomous driving on drivers’ workload and acceptance, and suggest how improvements in driver–AV interaction can be made.