AASHTO TP 143-21 PDF Download

The Standard Method of Test for Continuous Measurement of Sideway-Force Friction Number for Highway Pavements, also known as AASHTO TP 143-21, is a test method that measures the sideway-force friction of paved surfaces using a tire mounted at a 20-degree angle. The test is conducted by operating a device that contains one freely rotating test wheel angled at 20 degrees to the direction of motion, and is operated over a pavement surface at operating speed while the test wheel is under a vertical load.

The test equipment has been built onto various vehicle chassis and can function independently of the vehicle used. This method collects data on the sideway-force friction, as well as other data, along the entire length of the pavement surface being tested. The purpose of collecting this data is to compare the frictional properties of a pavement relative to other pavements, or to evaluate changes in these frictional properties over time. It is important to note that the data obtained from this test method are not sufficient to determine the stopping distance required for a vehicle on either a wet or dry pavement.