What does the tread wear number mean on a tyre?

The tread wear number on a tire, part of the Uniform Tire Quality Grading (UTQG) system, indicates the expected longevity of the tire's tread compared to a reference tire. A higher number signifies a longer tread life; for example, a tire rated at 400 should last twice as long as one rated at 200. However, actual wear can vary based on driving conditions, maintenance, and tire usage. It's essential to consider this number alongside other factors like traction and temperature ratings for a comprehensive evaluation of tire performance.