Most modern cars are equipped with advanced driver assistance systems (ADAS) dedicated to driver safety. For example, the lane departure warning system will sound an alert regardless of whether the vehicle deviates laterally from the white line intentionally or unintentionally. Designed to prevent veering off course due to distraction or drowsiness.
Research confirms that such systems can indeed prevent collisions. However, some drivers find wink-and-jab driving behavior annoying and often unnecessary. Recently, a well-designed study showed that using such systems also changes driving behavior, often for the worse.
The study, conducted by university researchers in the United States and Hong Kong, drew from telematics data collected in the United States by an unnamed large automaker. This telematics data is widely collected by automakers, prompting measures to protect driver privacy. These data provide information on vehicle performance (such as speed and acceleration) and vehicle journey (such as when and where the vehicle traveled).
The data also provides aggregated details on driver attributes such as age, gender and income level. By tracking the age of the vehicles in the study, researchers can also see how driver behavior changes over time.
The authors set out to distinguish the impact of two types of ADAS on drivers: those that require immediate corrective action and those that merely provide information. They predicted that drivers using only ADAS that require immediate corrective action would operate less cautiously than without ADAS, whereas drivers using only informational alerts would be more cautious. And it turns out that's true.
As examples, they highlighted demanding ADAS systems, including forward collision warning systems, which sound an alert when the system concludes the vehicle may be in collision with an object ahead, and the aforementioned lane departure warning systems. They found that in the United States, the two systems are almost always bundled.
Researchers test sensor-based ADAS features such as forward collision and lane departure warning systems
As an example of information-only ADAS, they looked at cars equipped only with blind-spot detection, which was limited to flashing a visual alert when another car was approaching from behind.
They used a control group of cars that were not equipped with any of the above ADAS systems. These three samples totaled 195,743 vehicles, distributed across the United States.
To assess driver behavior, the study focused on speed and braking. When it comes to speed, the focus of the study is not whether drivers were speeding, but how fast they were driving compared to the average speed of all drivers on the same stretch of road.
Speeding is defined as driving more than one standard deviation faster than the average speed. Emergency braking is defined as deceleration exceeding 6 miles per second (10 kilometers per hour).
"The reduction in emergency braking and speeding incidents indicates an improvement in overall driving behavior," the authors observed.
The study found that drivers who only used forward collision and lane departure warnings had about 5 percent more speeding accidents and about 6 percent more emergency braking accidents each day than drivers who didn't use ADAS at all.
In comparison, drivers who only used blind spot detection experienced 9% fewer speeding accidents and nearly 7% fewer emergency braking accidents compared to drivers who did not use ADAS.
Both effects increased slightly over time. In speculating on the cause of these behavioral effects, the authors proposed that ADAS prompts requiring drivers to take urgent action trigger so-called System 1 cognitive processing, which is rapid and automated. Drivers who react in this way may view frequent warnings as a sign that ADAS is improving safety and therefore be more willing to reduce their level of caution.
They propose that information-only ADAS such as blind spot detection are more likely to produce System 2 thinking, where people reflect on their experiences, learn from them and deliberately adjust their behavior.
To test these ideas, they compared the behavior of men and women using each system. They said multiple studies have shown that women are slower than men to increase risk when encountering emergency ADAS prompts and are faster than men to learn reflectively from information prompts. Sure enough, this gender difference showed up in the results.
It is worth emphasizing that both types of ADAS systems remain effective in reducing collisions even if reported behavior changes. The authors report that forward collision and lane departure warning combined reduced collision rates by 15 percent, and blind spot monitoring reduced crash rates by 19 percent.
However, they said car companies should think about how to mitigate the negative impact of emergency ADAS warnings on behavior. We hope their research will lead to the development of systems that reduce harsh ringing and beeping.
The study, titled "General behavioral effects of intelligent system warnings: the case of advanced driver assistance systems," was published in the journal Production & Operations Management.