Analysis of Disengagements in Semi-Autonomous Vehicles: Drivers’ Takeover Performance and Operational Implications

This report analyzes the reactions of human drivers placed in simulated Autonomous Technology disengagement scenarios. The study was executed in a human-in-the-loop setting, within a high-fidelity integrated car simulator capable of handling both manual and autonomous driving. A population of 40 individuals was tested, with metrics for control takeover quantification given by: i)    response times (considering inputs of steering, throttle, and braking); ii) vehicle drift from the lane centerline after takeover as well as overall (integral) drift over an S-turn curve compared to a baseline obtained in manual driving; and iii) accuracy metrics to quantify human factors associated with the simulation experiment. Independent variables considered for the study were the age of the driver, the speed at the time of disengagement, and the time at which the disengagement occurred (i.e., how long automation was engaged for). The study shows that changes in the vehicle speed significantly affect all the variables investigated, pointing to the importance of setting up thresholds for maximum operational speed of vehicles driven in autonomous mode when the human driver serves as back-up. The results shows that the establishment of an operational threshold could reduce the maximum drift and lead to better control during takeover, perhaps warranting a lower speed limit than conventional vehicles. With regards to the age variable, neither the response times analysis nor the drift analysis provide support for any claim to limit the age of drivers of semi-autonomous vehicles.

Video: Dr. Francesca Favaro discusses her current MTI research project and the work she does on autonomous systems

 

University: 

Mineta Consortium for Transportation Mobility
San José State University

Principal Investigator: 

Francesca Favaro, Ph.D.

PI Contact Information: 

Mineta Transportation Institute
San José State University
210 N. 4th St., 4th Floor
San José, CA 95112
francesca.favaro@sjsu.edu 

Funding Source(s) and Amounts Provided (by each agency or organization): 

U.S. Department of Transportation, Office of the Assistant Secretary for Research and Technology – $73,498.02 

Total Project Cost: 

$73,498.02

Agency ID or Contract Number: 

69A3551747127

Dates: 

September 2017 to June 2019

Implementation of Research Outcomes: 

This study analyzed the interaction between human drivers and semi-automated vehicles. In particular, it tested the performance of the human driver in taking back control and recovering from failures of the autonomous technology. The study tested a population of 40 individuals within a human-in-the-loop simulator, where drivers set in a physical car (a BMW 6 series) surrounded by a 220 degree curved screen and 3-fold rear panels that simulated the external environment.  The study investigated novel variables to quantify the quality of control takeover such as the dependance of reaction times and vehicle lateral drift on the age of the driver, the speed at the time of disengagement, and the time at which the disengagement occurred (i.e., how long automation was engaged for). 

Impacts/Benefits of Implementation: 

The observed results point to the importance of setting up thresholds for maximum operational speed of vehicles driven in autonomous mode when the human driver serves as back-up, perhaps warranting a lower speed limit than conventional vehicles. This research shows that the establishment of an operational threshold could reduce the maximum drift and lead to better control during takeover after a failure. Unintentional drift also attests to the needs for discussions on possible dedicated lane usage for autonomous vehicles and separation from conventional traffic, as well as for the possibility of increasing lane width in dedicated lanes for semi-autonomous vehicles. With regards to the age variable, neither the response times analysis nor the drift analysis provide support for any claim to limit the age of drivers of semi-autonomous vehicles.

Project Number: 

1710