Transition to manual: Driver behaviour when resuming control from a highly automated vehicle

• Published in: Transportation research. Part F, Traffic psychology and behaviour Vol. 27; pp. 274 - 282
• Main Authors: Merat, Natasha, Jamson, A. Hamish, Lai, Frank C.H., Daly, Michael, Carsten, Oliver M.J.
• Format: Journal Article
• Language: English
• Published: Elsevier India Pvt Ltd 01.11.2014
• Subjects: Automated; Automation; Control systems; Disengaging; Driver behaviour; Drivers; Eye tracking; Highly automated driving; Level 3 automation; Manual control; Roads; Transition time; Vehicles; Transition time; Highly automated driving; Level 3 automation; Driver behaviour; Eye tracking
• ISSN: 1369-8478; 1873-5517
• DOI: 10.1016/j.trf.2014.09.005

•A driving simulator study was conducted to study drivers’ ability to resume control from an automated system.•Disengagement of automation was either at a fixed or variable pace.•Eye tracking was used to initiate variable disengagement.•Vehicle and eye-tracking measures suggest drivers take ∼15s to resume control and up to 40s to stabilise vehicle control.•The implications of these results for designing suitable Human Machine Interfaces in automated vehicles are discussed. A driving simulator study was designed to investigate drivers’ ability to resume control from a highly automated vehicle in two conditions: (i) when automation was switched off and manual control was required at a system-based, regular interval and (ii) when transition to manual was based on the length of time drivers were looking away from the road ahead. In addition to studying the time it took drivers to successfully resume control from the automated system, eye tracking data were used to observe visual attention to the surrounding environment and the pattern of drivers’ eye fixations as manual control was resumed in the two conditions. Results showed that drivers’ pattern of eye movement fixations remained variable for some time after automation was switched off, if disengagement was actually based on drivers’ distractions away from the road ahead. When disengagement was more predictable and system-based, drivers’ attention towards the road centre was higher and more stable. Following a lag of around 10s, drivers’ lateral control of driving and steering corrections (as measured by SDLP and high frequency component of steering, respectively) were more stable when transition to manual control was predictable and based on a fixed time. Whether automation transition to manual was based on a fixed or variable interval, it took drivers around 35–40s to stabilise their lateral control of the vehicle. The results of this study indicate that if drivers are out of the loop due to control of the vehicle in a limited self-driving situation (Level 3 automation), their ability to regain control of the vehicle is better if they are expecting automation to be switched off. As regular disengagement of automation is not a particularly practical method for keeping drivers in the loop, future research should consider how to best inform drivers of their obligation to resume control of driving from an automated system.