Title: The effects of driving with different levels of unreliable automation on self-reported workload and secondary task performance

Authors: J.C.F. De Winter; N.A. Stanton; J.S. Price; H. Mistry

Addresses: Faculty of Mechanical, Maritime and Materials Engineering, Department of BioMechanical Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands ' Transportation Research Group, Faculty of Engineering and the Environment, Boldrewood Innovation Campus, University of Southampton, Burgess Road, Southampton, SO16 7QF, UK ' Transportation Research Group, Faculty of Engineering and the Environment, Boldrewood Innovation Campus, University of Southampton, Burgess Road, Southampton, SO16 7QF, UK ' Transportation Research Group, Faculty of Engineering and the Environment, Boldrewood Innovation Campus, University of Southampton, Burgess Road, Southampton, SO16 7QF, UK

Abstract: Until automated cars function perfectly, drivers will have to take over control when automation fails or reaches its functional limits. Two simulator experiments (N = 24 and 27) were conducted, each testing four automation levels ranging from manual control (MC) to highly automated driving. In both experiments, participants about once every 3 min experienced an event that required intervention. Participants performed a secondary divided attention task while driving. Automation generally resulted in improved secondary task performance and reduced self-reported physical demand and effort as compared to MC. However, automated speed control was experienced as more frustrating than MC. Participants responded quickly to the events when the stimulus was salient (i.e., stop sign, crossing pedestrian, and braking lead car), but often failed to react to an automation failure when their vehicle was driving slowly. In conclusion, driving with imperfect automation can be frustrating, even though mental and physical demands are reduced.

Keywords: self-reported workload; automated driving; secondary tasks; automation levels; critical events; ACC; adaptive cruise control; automated steering; human factors; unreliable automation; simulation; driver intervention; divided attention; automated speed control; manual control; vehicle control; mental demands; physical demands; driving demands; automated vehicles; autonomous vehicles; automated cars.

DOI: 10.1504/IJVD.2016.076736

International Journal of Vehicle Design, 2016 Vol.70 No.4, pp.297 - 324

Received: 10 Jan 2015
Accepted: 14 Nov 2015
Published online: 24 May 2016 *

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