Researchers at Chalmers University of Technology in Gothenburg, Sweden, say they have solved a 70-year old mystery in traffic research: the inexplicable jerkiness that drivers exhibit while steering a vehicle.

The discovery may lead to safety systems in cars that can correct dangerous steering movements before they occur, researchers said. Applications include smarter anti-skid systems and systems for fatigued drivers.

“Imagine a fatigued driver on the verge of running off the road,” researcher Ola Benderius said. “He or she suddenly wakes up and reflexively initiates a very large corrective maneuver, a potential misjudgment that can lead to something very dangerous. Since we are now able to predict how far the driver is going to turn the wheel, the vehicle’s support systems can identify potential misjudgments and intervene, which means a serious accident, such as the car traveling into approaching traffic, can be avoided.”

The discovery is related to innate human behavior.

As early as 1947, British researcher Arnold Tustin produced the first model for how a person steers towards a target. He identified a continuous and linear control behavior. When a car is driven, this corresponds to the driver gently and continuously following the road with the steering wheel. This behavior theory, known as “tracking,”has been the prevailing theory for car driving ever since.

However, when comparing the linear model with actual measured data, some deviations become apparent – namely jerkiness in the steering signal. Tustin saw these deviations from the continuous prediction as well, but the mystery long remained unsolved.

Benderius and his colleague Gustav Markkula began to view the mystery differently while attending a lecture on neurocognition at Sahlgrenska University Hospital. The lecture addressed behavioral theory related to how people reach for something. 

When studying how humans move their hand from Point A to pick up something from Point B, scientists have discovered that the speed of the movement has a direct relationship with the distance. The longer the distance, the quicker the movement. The interesting effect of this is that the time for the movement is the same, regardless of the distance.

”We immediately recognized this pattern from our measured steer signals,” Benderius said. ”It was a bit of a eureka moment. Was it possible that this basic human behavior also controlled how we steer a car?”

With the idea in mind, Benderius extracted over 1,000 hours of car and truck driving from real driving data, which resulted in 1.3 million steer corrections. It turned out that 95 percent of these correspond with the reaching theory.

Benderius and Markkula concluded that steering is not linear when the driver follows the road. Instead, the driver turns the wheel according to the special reaching pattern. 

“Rather than looking upon steering as continuously following the road, steering corrections seem to be applied in a very predetermined manner,” Benderius explained. “The control behavior has also proven to be very natural. I saw this in an earlier study where I examined driving behavior in 12-year-olds and their parents.”

This revelation helped Benderius develop a mathematical model that can explain many observed steering behaviors. As a result, driver response to different situations can be predicted before it occurs. Benderius said he believes the discovery can have an impact on an entire research field. 

“Control behavior has traditionally been studied on the basis of control theory and technical systems,” Benderius said. “If it is instead studied on the basis of neuroscience with focus on the human, an entire new world opens up. This could push the research field in an entirely different direction.”