Taking back control of an autonomous car affects human steering behavior

December 6, 2016, Stanford University
Holly Russell, former graduate student in the Dynamic Design Lab, is lead author of a new study on the handover of control from an autonomous car to a human driver. She is shown in Stanford's X1 experimental vehicle. Credit: Steve Castillo

There you are, cruising down the freeway, listening to some tunes and enjoying the view as your autonomous car zips and swerves through traffic. Then the fun ends and it becomes time take over the wheel. How smooth is that transition going to be?

Twenty-two drivers put that question to a test—on a track, not a freeway—to find out. The results, which were published in the first issue of Science Robotics on Dec. 6, could help in the design of future .

The researchers, who had a combined expertise in autonomous car design, human-robot interaction research and neuroscience, found that the transition could be rough. Drivers who experienced certain changes in since their last time at the wheel, such as changes in speed, since their last time at the wheel had a period of adjustment in their steering.

"Many people have been doing research on paying attention and situation awareness. That's very important," said Holly Russell, lead author of the research and former graduate student in the Dynamic Design Lab at Stanford University. "But, in addition, there is this physical change and we need to acknowledge that people's performance might not be at its peak if they haven't actively been participating in the driving."

The trouble the drivers had getting used to different driving conditions wasn't enough to cause them to miss their turns, but it was noticeable in the researcher's measurements and by watching them wobble the wheel to account for over- and understeering. These challenges bring up the possibility that, depending on the particulars of the driver, the driving conditions and the autonomous system being used, the transition back to driver-controlled driving could be an especially risky window of time.

Mimicking a transition from self-driving

Study participants drove a 15-second course consisting of a straightaway and a lane change. Then they took their hands off the wheel and the car took over, bringing them back to the start. After going through this process four times, they drove the course 10 additional times with steering conditions that were modified to represent changes in speed or steering that may occur while the car drives itself.

Changing the steering ratio from the standard 15:1 to 2:1 simulated the more sensitive steering feel drivers experience at a higher speed. This modification made the car turn more sharply to simulate the way less steering wheel movement is needed to make a lane change at a high speed versus at a low speed.

All drivers were given advance warning of the changes and had some opportunity to probe the difference during the straightaway. Regardless, during the altered steering ratio trials, the drivers' steering maneuvers differed significantly from their paths previous to the experimental modifications.

"Even knowing about the change, being able to make a plan and do some explicit motor planning for how to compensate, you still saw a very different steering behavior and compromised performance," said Lene Harbott, co-author of the research and research associate in the Revs Program at Stanford.

The participants also drove the course another six times, after being taken back to the start by the car, with the original conditions restored. Again, drivers who experienced the steering ratio change displayed a clear period of adjustment, undershooting the steering wheel turning required to complete their .

In neuroscience this is explained as a difference between explicit and implicit learning, said IIana Nisky, co-author of the study and senior lecturer at Ben-Gurion University in Israel. Even when a person is aware of a change, their implicit motor control is unaware of what that change means and can only figure out how to react through experience.

A classic neuroscience test

This driving test is close to a real-life version of a classic neuroscience experiment that assesses motor adaptation. In one example of these experiments, participants use a hand control to move a cursor on a screen to specific points. The way the cursor moves in response to their control is adjusted during the experiment and they, in turn, change their movements to make the cursor go where they want it to go.

Just as in the driving test, people who take part in this experiment have to adjust to changes in how the controller moves the cursor. They also must adjust a second time if the original response relationship is restored.

"Even though there are really substantial differences between these classic experiments and the car trials, you can see this basic phenomena of adaptation and then after-effect of adaptation," said Nisky. "What we learn in the laboratory studies of adaptation in neuroscience actually extends to real life."

It also showed that the effect and after-effect of motor adaptation applies to skilled tasks that people have learned over a long period of time.

What this means for autonomous cars

Although these drivers were not so thrown off by the changes in steering that they drove off-course, the fact that there is a period of altered behavior is still significant. There are so many different variables involved in driving that anything that compromises driving performance could lead to an accident.

In this research, the test vehicle was developed at Stanford and doesn't represent any system currently available. The study addressed one specific example of handover, but there is still a lot to learn about how people respond in other circumstances, depending on the type of car, the driver and how the driving conditions have changed.

"If someone is designing a method for automated vehicle handover, there will need to be detailed research on that specific method," said Harbott. "This study is tip of an iceberg."

Explore further: BMW shows off concept car for the self-driving future

More information: "Motor learning impacts car-to-driver handover in automated vehicles," Science Robotics, robotics.sciencemag.org/lookup … /scirobotics.aah5682

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9 comments

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snoosebaum
not rated yet Dec 06, 2016
whats going to happen after i wake up from my snooze , or having a beer ?
dogbert
5 / 5 (1) Dec 06, 2016
Changing the steering ratio from the standard 15:1 to 2:1 simulated the more sensitive steering feel drivers experience at a higher speed.


Changing the steering ratio is not something which a driver would need to adjust to when talking over steering from a self driving car. It is a meaningless test.

The real problems associated with taking control from an autonomous vehicles have to do with the fact that the driver has not built and maintained a mental model of the road, the vehicles on the road, and their positions and velocity. The driver taking over is essentially blind to those factors.
JamesG
5 / 5 (2) Dec 06, 2016
Who in their right mind doesn't think most people in these things will just fall asleep or start reading a book, or eating, or putting on makeup. They are going to be treated as a release from the responsibility of driving by a huge portion of the public. People are lazy. Researchers are giving the public too much credit for being responsible.
dogbert
5 / 5 (2) Dec 06, 2016
The semiautonomous vehicles are dangerous because a non-driving driver cannot remain vigilant when not performing driving duties.
SciTechdude
5 / 5 (2) Dec 06, 2016
Yeah, the second a computer takes over you're going to zone out immediately and whip out your phone, or zonk right out. Sometimes only the sheer fear of death can keep someone driving as it is, take that away, zzzz.
ab3a
5 / 5 (3) Dec 06, 2016
As we saw with the Air France 447 tragedy, when heavily automated systems fail, humans have a very hard time taking over and doing even the most basic things. In the latter case, the co-pilot held the aircraft in a stall by keeping backpressure on the stick --something that every student pilot is taught not to do when recovering from unusual attitudes (and this is part of the check ride give to every private pilot).

The co-pilot was no slouch of a pilot. He was a stressed and slightly fatigued man who frankly didn't understand what the situation was.

And we expect casual drivers to do better with less time? I don't think that's going to work too well.
BackBurner
5 / 5 (1) Dec 06, 2016
It should be obvious any system intended to make humans unnecessary should succeed completely in doing that. If a driver needs to "take over", the system doesn't work.

A few years (maybe decades) ago a 757 flew into a mountain with a flight crew aboard. Programmed wrong by the pilot. Imagine that. For what had to be several minutes the crew watched the plane fly itself into dirt.
adam_russell_9615
5 / 5 (1) Dec 07, 2016
from NY Times
But Google decided to play down the vigilant-human approach after an experiment in 2013, when the company let some of its employees sit behind the wheel of the self-driving cars on their daily commutes. Engineers using onboard video cameras to remotely monitor the results were alarmed by what they observed — a range of distracted-driving behavior that included falling asleep. "We saw stuff that made us a little nervous," Christopher Urmson, a former Carnegie Mellon University roboticist who directs the car project at Google, said at the time. The experiment convinced the engineers that it might not be possible to have a human driver quickly snap back to "situational awareness," the reflexive response required for a person to handle a split-second crisis.

www.nytimes.Com/2...car.html
Eikka
not rated yet Dec 07, 2016
Changing the steering ratio is not something which a driver would need to adjust to when talking over steering from a self driving car. It is a meaningless test.


The steering ratio change was used to simulate the fact that the car steers more or less rapidly depending on how fast it's going. Smaller steering action at a higher speed result in the same turning rate because the wheels are spinning faster.

They most likely chose to do it that way because a person is going to be speed-blind after not having paid attention to what's going around the car, so they either don't know or can't tell how fast they're going, so they don't have the intuition of how the car is going to respond to steering.

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