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ASTM E1960-07(2023)

Current Reaffirmation

Standard Practice for Calculating International Friction Index of a Pavement Surface

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1.1 This practice covers the calculation of the International Friction Index (IFI) from a measurement of pavement macrotexture and wet pavement friction. The IFI was developed in the PIARC International Experiment to Compare and Harmonize Texture and Skid Resistance Measurements. The index allows for the harmonizing of friction measurements with different equipment to a common calibrated index. This practice provides for harmonization of friction reporting for devices that use a smooth tread test tire.

1.2 The IFI consists of two parameters that report the calibrated wet friction at 60 km/h (F60) and the speed constant of wet pavement friction (Sp).

1.3 The mean profile depth (MPD) has been shown to be useful in predicting the speed constant (gradient) of wet pavement friction.2

1.4 A linear transformation of the estimated friction at 60 km/h provides the calibrated F60 value. The estimated friction at 60 km/h is obtained by using the speed constant to calculate the estimated friction at 60 km/h from a measurement made at any speed.

1.5 The values stated in SI (metric) units are to be regarded as standard. The inch-pound equivalents are rationalized, rather than exact mathematical conversions.

1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.


5.1 This is the practice for calculating the IFI of the pavement. The IFI has proven useful for harmonization of the friction measuring equipment. F60 and Sp have proven to be able to predict the speed dependence of wet pavement-related measurements of the various types of friction-measuring equipment.2 The two IFI parameters (F60 and Sp) have been found to be reliable predictors of the dependence of wet pavement friction on tire slip and vehicle speed.

5.2 The IFI parameters, F60 and Sp, can be used to calculate the calibrated friction at another slip speed using a transformation equation.

5.3 The IFI model given below describes the relationship between the values of wet pavement friction FRS measured at a slip speed of S and between the friction values measured by different types of equipment.

5.4 A significance of the IFI model is that the measurement of friction with a device does not have to be at one of the speeds run in the experiment. FRS can be measured at some S and is always adjusted to FR60. Thus, if a device cannot maintain its normal operating speed and must run at some speed higher or lower because of traffic, the model still works well. In that case, S is determined by the vehicle speed (V) which can be converted to S by multiplying V by the percent slip for fixed slip equipment or by multiplying V by the sine of the slip angle for side force equipment.

5.5 This practice does not address the problems associated with obtaining a measured friction or measured macrotexture.

SDO ASTM: ASTM International
Document Number E1960
Publication Date May 1, 2023
Language en - English
Page Count 5
Revision Level 07(2023)
Supercedes
Committee E17.21
Publish Date Document Id Type View
April 1, 2007 E1960-07 Revision
Aug. 10, 2003 E1960-03E01 Revision
Aug. 10, 2003 E1960-03 Revision
July 10, 1998 E1960-98 Revision
May 1, 2023 E1960-07R23 Reaffirmation
Sept. 1, 2015 E1960-07R15 Reaffirmation
Sept. 1, 2011 E1960-07R11 Reaffirmation