If all new tires are not equal, worn tires are even harder to compare.
Michelin conducted internal tests that compared braking distances among specific tires in new and worn conditions to reveal how safety performance changes over time. The "worn" tires were buffed to the tread wear indicator, near the end of the tire's useful life (at 2/32-inch, as defined in many states).
The test results are dramatic. Some worn tires deliver wet-braking distances that are about the same or better than other new tires. In fact, there was a 78-foot difference in stopping distance, more than five car lengths, between the best and worst tire in the test.