New York, Dec 13 (IANS) After allowing drivers to test retaking control of an autonomous car on a track, researchers found the transition could be risky.

Twenty-two participants drove a 15-second course consisting of a straightaway and a lane change, then took their hands off the wheel and the self-drive car took over, bringing them back to the start.

After going through the process four times, they drove the course 10 additional times with steering conditions that were modified to represent changes in speed or steering, Xinhua news agency reported.

It was noticeable under the researchers' watch that the drivers wobble the wheel to account for over- and understeering, according to a study published last week in the first issue of Science Robotics.

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.

"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."