Toronto, Ontario — Sharp curves in the road may pose a challenge for advanced driver assist features and potentially limit their safety benefits, according to a new study from the Insurance Institute for Highway Safety (IIHS).
To conduct the study researchers used on-board data-acquisition systems that collected information from two 2016 Land Rover Range Rover Evoque and two 2017 Volvo S90 vehicles driven by 39 drivers over four weeks.
The Evoques were equipped with ACC, and the S90s were equipped with both ACC and Volvo’s Pilot Assist partial automation system — which combines ACC and lane centering.
Analyzing the data, the researchers found that ACC or Pilot Assist were less likely to be active as curves became sharper. In the Evoque vehicles, drivers were 72 percent less likely to use ACC on the sharpest category of curves (those with a radius smaller than 2,292 feet) than they were to use those features on straight road segments. In the S90 vehicles, drivers were 75 percent less likely to use Pilot Assist and 66 percent less likely to use ACC on the sharpest curves.
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, either because drivers switch the features off or they deactivate automatically.
“We know that advanced driver assistance features may help prevent crashes, but obviously they can only do so if drivers use them,” says IIHS Senior Research Transportation Engineer Wen Hu, the lead author of the paper. “This study suggests that these technologies will only be able to reach their full potential if drivers can trust them to handle curves.”
The researchers did not determine in this analysis whether the driver switched off the system or it 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. ACC deactivates when a driver applies the brakes.
“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,” says Hu.