A new study from the IIHS claims that those who use adaptive cruise control tend to accelerate more than those who don’t.
To analyze how people drive with adaptive cruise control, the IIHS delivered a 2016 Land Rover Range Rover Evoque and a 2017 Volvo S90 to 40 different drivers in the Boston area for four consecutive weeks. Both were equipped with adaptive cruise control systems. The drivers covered approximately 20,000 miles in total.
Ultimately, drivers with adaptive cruise at 24% more likely to speed on highways than drivers with the system disabled. The definition of “speeding offenses” used here is any amount that exceeds the posted speed limit. In addition to driving more time over the speed limit, drivers using adaptive cruise control speeded to a greater extent than those who did not use it. The difference was only 0.9 mph – 6.1 mph more than the average 7.0 mph – but enough to stand out in the study, and enough, says the IIHS, to significantly increase the risk of accidents. injuries and fatalities to match.
However, the IIHS also refers to previous data showing that the use of systems such as adaptive cruise control and lane assistance reduces the risk of an accident. Whether the higher speeds offset the security blanket these systems provide is yet to be determined.
The IIHS didn’t come to any firm conclusions about why people speed up more when using adaptive cruise control, but there are some educated guesses. First, both cars used in the study allow people to adjust their speed in 5 mph increments. This could encourage someone to theoretically set their speed to 75 mph or 80 mph in a 70 mph zone – the study found clusters of speed behavior centered around these 5 mph steps. Meanwhile, someone taking manual control of the speed will likely oscillate somewhere between 70 mph and 80 mph as they move.
This study also discussed the possibility of curbing adaptive cruise control speeds by limiting what speeds the system could be set to. For example, a vehicle can allow the system to take full advantage of its adaptive cruising speed at the specified speed limit. The study (and we agree) suggests that people just wouldn’t use the system if it shut them out from speeding and ultimately get nowhere.
Many people also use adaptive cruise to keep up with traffic during heavy commutes. If you do not set the target speed high enough, you will not keep up with the vehicle in front as the traffic accelerates and slows down. It’s a tricky balance, but one that could encourage faster speeds.
There aren’t many useful conclusions from this study, but it’s a conversation starter. The use of systems marketed as “safety systems” as a speeding aid is worth talking about, and is likely to be a topic for future studies.