Study: Driver assist system warnings can lead to worse driving

Despite automakers’ efforts to improve vehicle occupants’ safety by implementing driver assist system tools and warnings, these may sometimes have the opposite effect – distracting drivers and even endangering lives, a recent study has suggested.

Indeed, driver assist system proponents have pointed to studies showing that blind spot and lane departure warnings decrease collisions, but skeptics argue it may make drivers less attentive as they rely too much on warning signals, and new research has indicated the latter might be correct in certain cases.

According to Ashish Agarwal, associate professor of information, risk, and operations management at the McCombs School of Business at The University of Texas at Austin, there’s evidence for both viewpoints, which he shared in a video streamed on July 10.

As it happens, Agarwal worked with Cenying Yang of the City University of Hong Kong and Prabhudev Konana of the University of Maryland to analyze data from onboard sensors on a prominent manufacturer’s cars sold in 2018 and 2019, which included trips, speeds, and accelerations rates. 

Out of the 195,743 vehicles tested in the study, some had Advanced Driving Assistance Systems (ADAS), and some did not. The researchers’ main question was: Do these systems affect the general driving behavior of users over time and if so, how?

The team gauged two types of hazardous driving behavior – hard braking and speeding, as well as zeroed in on two sets of ADAS features that require driver response  – blind spot detection and lane departure / forward collision warnings. As Agarwal explained:

“We compared cars with blind spot detection with the ones that don’t have that to see how it influences speeding and hard braking behavior.”

Results of driver assist system analysis

According to the results, the two kinds of warning signals had opposite effects on driving behavior. In terms of blind spot detection, it reduced the daily number of hard braking events by 6.76% and speeding events by 9.34% compared to cars without ADAS. However, lane departure / forward collision alerts triggered 5.65% more hard braking and 5.34% more speeding incidents.

Meanwhile, time tended to magnify both effects as drivers became accustomed to the systems. In other words, drivers would accelerate 0.40% less often for every extra month they used blind spot detection. That said, they would speed 0.32% more for each added month with lane departure warnings.

To understand why different features trigger distinct behaviors, Agarwal and his colleagues have suggested a psychological concept called dual process theory, which means these features prompt two divergent modes of thinking. 

Specifically, urgent warnings (like lane departure and forward collision) require a driver to correct course immediately, which causes System 1 or reactive thinking – automatic and largely unconscious. In Agarwal’s words, “It triggers risk compensation behavior, which impedes your learning and makes your behavior worse.”

By contrast, blind spot detection doesn’t demand instant reaction and allows time for System 2 or deliberate thinking, reasoning one’s way to a response, and encourages learning and driving behavior correction. As Agarwal opined, “For learning to take place, you need to be in the System 2 mode. (…) That means that you learn, and your behavior improves over time.”

Elsewhere, the automotive industry seems to be speeding towards autonomy in cars, including Mercedes Benz, which has gained approval to test autonomous driving indicator lights in Germany, the first time ever that any automaker received this approval.