That rating grades the tire’s coefficient of friction with a locked-up tire, traveling 40 mph on a wet surface. A situation that used to happen in the days before anti-lock brakes when the driver would slam on the brakes in a panicked braking situation, essentially locking up the wheel and skidding to a stop. It was more a test of the tire’s materials than it was of the tire’s tread pattern since it was only testing a non-rolling tire. Back in those days, this was useful information about a tire. With the anti-lock braking systems in today’s modern cars, that rating is now antiquated and meaningless since tires are no longer subjected to those conditions. ABS prevents the tires from locking up, even when you push the brake pedal to the floor. I can see where it would be a useful rating if you were choosing tires for your 1960s muscle car or for your trailer that has brakes but not ABS. When choosing tires for a modern and capable CX-5, I wouldn’t pay too much attention to the traction rating of a tire.