Uniform Tire Quality Grading (UTQG)
The Uniform Tire Quality Grading rating is a quality rating system developed by the Department of Transportation. It is designed to tell consumers the relative performance of passenger tires (but does not apply to winter tires).
The "150" indicates the treadwear rating
the "A" indicates traction
the "B" indicates temperature
The Treadwear rating is based on a wear test performed on a 400 mile government test course covering specified sections of public roads in Texas. A group of not more than 4 test vehicles travels the course in a convoy so that all tires experience the same conditions. Tread groove depths of the tires being tested are measured after each 800 miles. The same procedure is followed for a set of "control" or "course monitoring tires" Upon the completion of the 7200 mile test, the rating results of both tires are compared, and the tires being tested are assigned a treadwear rating according to government standards. This number can be used to compare between tires. In the above example, this tire rated 150 should last 1/2 as long as a tire rated 300. The relative performance of tires depends upon the actual conditions of their use and may be significantly different from the norm due to differences in road characteristics and climate.
The Traction ratings are AA, A, B, and C, from highest to lowest. This measurement indicates a tires ability to stop in a straight line on wet pavement. The rating is based on a 40mph test where the brakes are "locked up" on wet asphalt and wet concrete surfaces. It's important to remember that this rating does not indicate the tires ability to resists hydroplaning, and do not apply to cornering traction.
Temperature ratings are determined by running tires on an indoor road wheel test under specified conditions. Successive 30-minute runs are made in 5mph increments starting at 75mph and continuing until the tire fails. Tires with an A rating must withstand at least 114mph, B at least 99mph, and C at least 85mph. These measurements indicate the tire's ability to sustain high temperatures, which often cause tires to wear away quickly or in extreme conditions lead to sudden tire failure.