AAA is warning drivers that worn tires can significantly increase a vehicle's stopping distance in wet conditions, even if the tread depth is considered safe.

Tests conducted by AAA compared new all-season tires to tires with a tread depth that had worn to 4/32 of an inch. Researchers found that the worn tires typically resulted in a 43 percent increase in stopping distance in wet conditions, adding an extra 87 feet before a car came to a full stop. Worn tires had a similar effect on light trucks, extending the average stopping distance by 86 feet.

"Even the most advanced safety systems rely on a tire's basic ability to maintain traction, and AAA's testing shows that wear has a significant impact on how quickly a vehicle can come to a stop in wet conditions to avoid a crash," said John Nielsen, AAA's managing director of automotive engineering and repair.

In partnership with the Automobile Club of Southern California's Automotive Research Center, AAA tested the different effects of worn and new tires on a 2017 Toyota Camry and a 2017 Ford F-150. Researchers used six different sets of tires, classifying three sets as high-priced and three as low-priced. Some tires were artificially worn to a tread depth of 4/32 to test the effect of this condition.

For the stopping distance test, researchers measured the time and distance it took for a vehicle to come to a stop. AAA said the ability to stop quickly can avoid or mitigate a collision, while an increased stopping distance can result in a more serious crash.

"AAA's testing demonstrates the impact that tire tread has on safety," said Megan McKernan, manager of the Automobile Club of Southern California's Automotive Research Center. "If tested side-by-side at 60 miles per hour, vehicles with worn tires would still be traveling at an alarming 40 miles per hour when reaching the same distance it takes for vehicles with new tires to make a complete stop."

The traction test also determined that worn tires reduced a car's handling ability by 33 percent on average. A light truck's handling ability was reduced by 28 percent. AAA said this effect can result in more instability during emergency maneuvers and make tires more likely to hydroplane.

Although tire effectiveness varied by brand, cost did not have any significant effect on a worn tire's performance. All tires demonstrated longer stopping distances and degraded handling in wet conditions when worn to a 4/32 tread depth.

AAA said that while drivers are frequently advised to replace tires when their tread depth reaches 2/32 of an inch, it is better to make the replacement when they are at 4/32 of an inch. Drivers can test this tread depth by putting a quarter into the groove upside-down; if the top of George Washington's head is visible, the tire has worn to a depth of at least 4/32.

In wet conditions, AAA advises drivers to increase their following distance and reduce their following distance to allow more time to respond to an unexpected situation. Drivers should also avoid hard braking or sharp turns.

Cruise control can make it more difficult to regain control of a vehicle during hydroplaning, so it is best to avoid use of this feature. If the vehicle starts to hydroplane, take your foot off the accelerator and steer in the direction you wish to go until traction is restored. Don't slam on the brakes, as this can cause the vehicle to skid.