Final answer:
Federal law designates tires as worn out when the tread depth reaches 2/32 of an inch. This standard is enforced to maintain safety on the road. The penny test is a quick way to check tread depth.
Step-by-step explanation:
Under federal law, the minimum tread depth at which all tires are considered worn out is 2/32 of an inch. This safety standard is important because adequate tire tread depth is essential for providing traction to prevent hydroplaning in wet conditions and to maintain a safe stopping distance. When a tire's tread depth reaches this minimum, it is legally worn out and should be replaced to ensure the safety of the vehicle's operation.
To check tire tread depth, a simple test that can be used is the penny test. Insert a penny into the tread groove with Lincoln's head upside down. If you can see all of Lincoln's head, it's time to replace the tire because it's below the minimum tread depth. Regular monitoring of tire treads is an important aspect of vehicle maintenance and safety.