Standard Test Method for Skid Resistance Measurements Using the North Carolina State University Variable-Speed Friction Tester

1.1 This test method covers the measurement of skid resistance of paved surfaces or laboratory-prepared specimens using the North Carolina State University Variable-Speed Friction Tester.

1.2 The Variable-Speed Friction Tester (VST) is a pendulum-type tester with a locked-wheel smooth rubber tire at its lower end. A stream of water at a selected water test velocity is directed by a nozzle along the specimen surface in the path of contact between the locked-pendulum tire and the specimen. The friction between the tire and the specimen is measured from the energy lost in the pendulum. The tester is suitable for field tests on pavement surfaces as well as laboratory use (see Note 1).

1.3 The values measured, VSN (variable-speed (tester) number), represent the frictional properties obtained with the apparatus and procedures stated herein and do not necessarily agree or correlate directly with those obtained by other skid-resistance measuring methods.

Note 1—Uneven pavement surfaces in the field may provide inaccurate VSN measurements. Extreme care should be taken when using the VST in the field.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.