5.1 Friction characteristics of road surfaces are monitored by friction measurement systems, and the operating procedure for the use of these systems is found in Test Method E274. However, mechanical or electronic system anomalies, over time, could result in measurement errors or inaccuracies. This requires that each of these systems be evaluated, calibrated and correlated on a regular basis. The interval between calibrations depends on the frequency of use, maintenance and other factors. If any repairs are made to the system that may affect the calibration, the system should be recalibrated before further use. Generally, calibrations and correlations are recommended to be performed on an annual basis by one of the FTCs.

5.2 This guide defines the process of ensuring that Test Method E274 systems produce consistent and accurate data and correlating the Test Method E274 systems to national benchmark Test Method E274 systems.

1.1 This guide describes the evaluation, calibration, and correlation of Test Method E274 friction measurement systems as conducted at a Field Test Center (FTC).2 The evaluation, calibration and correlation process; using the specialized equipment, facilities, surfaces, trained personnel, and Area Reference Friction Measurement Systems (ARFMS) available at each FTC; are conducted using the procedures described below.

1.2 The FTC complies with the requirements of Guide E1890. Guide E1890 requires a more stringent calibration process and requires all ARFMS system be correlated together once a year on three surfaces at three speeds with twelve repeats each for a total of 108 pairs.

1.3 This guide is offered as a process to identify and quantify the variables that affect system performance, to minimize the effect of these variables, and to provide a means to relate Test Method E274 friction measurement systems to reference skid measurement systems.

1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.5 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.