Driving On Curves Using Automated Systems Can Pose Safety Challenges

Advanced driver assistance technologies like adaptive cruise control and more sophisticated partial automation systems are as much as 75% less likely to be active on sharp curves than on straight segments, limiting their potential safety benefits.

That is the main finding of a new study released earlier this month by the Insurance Institute for Highway Safety, a nonprofit financed by the insurance industry, which looked at how driving on curves in the road can constrain vehicle automation.  

“We know that advanced driver assistance features may help prevent crashes, but obviously they can only do so if drivers use them,” Wen Hu, senior research transportation engineer for the Insurance Institute and the lead author of the paper, said in a statement. “This study suggests that these technologies will only be able to reach their full potential if drivers can trust them to handle curves.”

Problems arise because adaptive cruise control (ACC) and more advanced partial automation that combines ACC with lane centering are often disabled on some of the sharper curves present on limited-access roadways, the researchers said, either because drivers switch the features off or they deactivate automatically.

The report noted that ACC works like conventional cruise control, but automatically slows the vehicle to maintain a preselected following distance from the vehicle ahead, “so the driver doesn’t need to repeatedly brake and reset the system.” And lane centering, it said, provides automated steering assistance designed to make sure the vehicle stays in the middle of the lane.

For the study, the researchers examined data collected from two 2016 Land Rover Range Rover Evoques equipped with ACC, and two 2017 Volvo S90 vehicles equipped with both ACC and Volvo’s Pilot Assist partial automation system, which combines ACC and lane centering. 

The vehicles were driven by 39 drivers over a four week period.

The results of the analysis indicated that both ACC and Pilot Assist were less likely to be active as curves became sharper. Evoque drivers were 72% less likely to use ACC on the sharpest category of curves than on straight road segments; the S90 drivers were 75% less likely to use Pilot Assist and 66% less likely to use ACC on the sharpest curves.

The study didn’t address whether the drivers switched off the systems or if they deactivated automatically. Lane centering can automatically become suspended when the driver manipulates the steering wheel or uses the turn signal, or when the system’s sensors cannot detect the lines painted on the road, and ACC deactivates when the driver applies the brakes, the report explained.   

“The fact that Pilot Assist was frequently inactive on the sharpest curves is an important limitation, since the kinds of crashes lane centering could help prevent are more likely to occur on curves than on straightaways,” Hu added. 

To learn more about the study, click here.