It may not even be designed to prevent a crash.
In the age of constant distraction, even behind the wheel, emergency braking systems are getting more important by the day. Essentially, these technologies come in two flavors. The first is of the collision mitigation variety, which will only lessen the severity of a crash to a love tap but not completely avoid contact. Then there is the collision avoidance system that does its best to keep from making contact with the car in front. As straight forward as it sounds, AAA found that the effectiveness of these systems can vary from car to car.
The organization conducted a study by putting a Honda Civic, Lincoln MKX, Subaru Legacy, Volkswagen Passat, and Volvo XC90 through 70 different trials designed to test the effectiveness of the systems. The first of the tests were conducted with a speed differential under 30 mph and unsurprisingly, the automatic braking systems outperformed the collision mitigation systems by preventing crashes 60% of the time. What AAA didn't expect was that the mitigation systems managed to complete the same feat 33% of the time. Next, speeds were cranked up to 45 mph and the bait car was left static. In this harsh scenario, the collision prevention systems avoided crashes 40% of the time and reduced speeds by 74% on average.
By comparison, the mitigation systems fared dismally, reducing impact speed by only 9%. Still, high speeds are a compounding factor in accident damage, and even a reduction in 10 mph for a car traveling 30 mph reduces accident severity by 50%. Even so, the results aren't meant to highlight the obvious fact that systems designed to prevent a crash are better than those that only lessen its severity. Instead, AAA wants to bring to light that not all crash systems are created equally, a fact that escapes many Americans who buy and may later rely on them to get out of a sticky situation. With 40% of Americans having full trust in these systems, this study should provide a wake up call. Oh, and put down that phone.