As most people who have used adaptive cruise control in traffic can no doubt appreciate, the most common event that required intervention was a car ahead cutting into the driver’s lane. These occurred about once every 8.6 miles, or 24.4 minutes, with 90 percent requiring intervention by the driver.

Inadequate lane centering was the next most common event, occurring once every 11.3 miles or 32.2 minutes. Seventy-two percent of those events also required intervention. Not resuming after coming to a halt happened 71 times, each of which required the driver to act. On 57 occasions, the lane keeping or adaptive cruise control deactivated, and there were 43 instances of a test car failing to adequately slow down, of which 70 percent required the driver to hit the brakes.

Hands-on versus hands-off

AAA found that the less-advanced systems that required a driver to keep their hands on the steering wheel experienced notable events at three times the frequency of hands-free systems. Hands-off systems only required intervention every 7.2 miles or 20.1 minutes, whereas the less advanced systems required intervention on average every 2.3 miles or 6.7 minutes. AAA also noted that the hands-off systems told the driver to put their hands back on the wheel every 5.5 miles (or 15.3 minutes) on average.

AAA has some recommendations based on its findings, which could also be categorized under common sense. When you’re behind the wheel of a vehicle, you should always remain alert, and AAA cautions that ADAS is “never a substitute for an engaged driver.” Don’t be distracted, especially by your smartphone. Read the car’s user manual and understand how, when, and where its systems can be expected to work. And set an appropriate following distance to the car ahead, even if it means more cut-ins.

The organization says it will encourage automakers to improve ADAS performance, especially cut-in response and lane-centering.