People operating self-driving cars need at least six seconds and some cues from the vehicle to “get back in the loop” and take control in time to avoid an accident, researchers say.
There are already partially self-driving cars on the road that offer some level of automation, including cruise control and technology to help steer and keep cars in a lane, the study team writes in the journal Injury Prevention.
“Currently, the technology is not quite at the level where it is safe for drivers to take any attention off the road,” said lead author Tyron Louw of the University of Leeds in England, adding that drivers should keep their eyes on the road at all times.
Future technologies may allow for more freedom for drivers, but this could lead to problems when drivers need to react to road hazards. “Of course, people will do different things while their car is driving itself, but our results show that it is crucial then that the car can get drivers’ attention where it needs to be as soon as possible,” Louw told Reuters Health by email.
To determine how disengaged drivers react to sudden danger, the study team conducted a series of driving simulations at the University of Leeds with 75 volunteers aged 21 to 69. Each run simulated a car on autopilot with lane-keeping doing 70 miles per hour in the center lane of a highway.
The researchers simulated the condition of a driver being distracted or looking away from the road by filling the screen with thick or lighter fog. In some conditions, the screen was also overlayed with quiz questions to complete. For comparison, one simulation run had no added distractions.
In the rest of the simulation runs, after drivers were distracted for a while, the visual impediment would clear and a hazard would appear ahead. The drivers then needed to resume manual control and respond to the danger to avoid a crash.
The type of distraction used beforehand affected where drivers looked once the screen cleared. Following thicker fog or fog plus a quiz, for instance, drivers spent a little extra time scanning the entire scene before focusing on the center of the road where the hazard was. But this difference resolved within 2 seconds and there was no effect on the likelihood of a crash.
There were also variations among individuals in how fast they focused on the center of the road. Drivers who looked at the scene with a steady gaze on the hazard were less likely to experience a crash, while those who spent more time looking around erratically were more likely to have an accident.
The researchers concluded that the car’s most important task was to direct the driver’s attention to the hazard as quickly as possible, so there would be less time wasted scanning the scene in a dangerous way.
Louw said that drivers who located the danger more quickly had more time to assess how to take back control and respond safely. Ideally, the warning system should alert drivers a minimum of six seconds before reaching a hazard, to provide adequate time to respond, the researchers conclude.
Marieke Martens, a professor at University of Twente in the Netherlands who studies self-driving vehicles, noted that semi-automated systems are becoming more common in cars, but that none of them work perfectly.
While many cars are advertised as self-driving, the systems can fail with little warning and it is not safe for drivers to look away from the road, warned Martens, who was not involved in the study.
“Even when having attention on the road but feet and hands off means that you have to understand what the car can and cannot do,” Martens said. She added that more advanced systems may be even more risky if they make drivers feel they can let their attention wander.
“It is imperative that drivers understand what they are buying with any car that claims to have self-driving features,” Louw said. “Overestimating how intelligent your self-driving car is could end in tragedy.”
