What condition regarding treadwear can lead to a tire being deemed as failed?

A tire may be deemed failed if the treadwear indicators are touching the road because this signifies that the tire has reached the minimum allowable tread depth. Treadwear indicators, also known as wear bars, are built into the tire to provide a clear visual cue when the tread has worn down to 2/32 inch (the legal minimum in many areas). When these indicators are flush with the tire surface, it indicates that there is insufficient tread remaining for safe operation, as adequate tread depth is crucial for maintaining traction and effective water evacuation, especially in wet conditions.

In contrast, while unevenly worn tread or a tread pattern that is not original may indicate issues, they don't inherently mean that the tire has reached a critical failure point. A tread depth of more than 4/32 inch, although generally acceptable, would not indicate failure. Thus, the primary reason a tire is deemed failed under these conditions is the critical nature of having the tread depth above the minimum level, as shown by the treadwear indicators contacting the road.