Measurement of surface skid resistance

Surface skid resistance is measured by self-powered mobile devices or towed mobile devices. Spot measurements or measurements over short road sections are usually carried out by the British pendulum or ether portable devices. 

The mobile devices are distinguished into two categories. The first category includes devices where the skid resistance is measured by an independent wheel moving at zero angles to the direction of travel. Measurements are taken while the wheel is fully locked (blocked). 

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BS 7941-2 2000 Methods for measuring the skid resistance of pavement surfaces. Test method for measurement of surface skid resistance using the GripTester braked wheel fixed shp device. 

The British pendulum was designed with the aim of providing a low-cost and portable apparatus for stationary measurements of slip/skid resistance of a surface in the field or in the laboratory. This test method provides a measure of frictional property, micro-texture in particular, of surfaces and may be used to determine the relative effects of various polishing processes on materials or material combinations. 

CEN EN 13036-4. 2011. Road and airfield surface characteristics - Test methods - Part 4 Method for measurement of slip/skid resistance of a surface - The pendulum test. Brussels CEN. 

The values shown in the table indicate that the material compacts to the desired level with a 5-ton vibrating compactor. Surface skid resistance of the sections was measured using a California portable skid tester in accordance with California test method 342 D. The skid values are comparable with published values for fresh-open or dense-graded asphaltic concretes. The friction values increased with increasing sulfur concentration. 

A substantial number of mobile devices for measuring surface skid resistance have been developed globally. The majority of them have been manufactured in European Union (EU) countries. A relevant EU survey identified and reported 21 mobile devices (TYROSAFE 2008). Table 16.5 presents 19 of those devices together with their basic characteristic features. 

The ASTM locked wheel skid tester or the pavement friction tester (PFT) was developed in America and is one of the first pavement surface skid resistance measuring devices. 

Texture depth directly affects the skid resistance of the pavement surface. In many countries, the minimum allowed texture depth is 0.5 mm. Pavement segments with values lower than 0.5 mm should be investigated immediately, along with skid resistance measurements, and restoration of the surface skid resistance should be programmed. 

CEN/TS 13036-2. 2010. Road and airfield surface characteristics — Test methods. Part 2 Assessment of the skid resistance of a road pavement surface by the use of dynamic measuring systems. Brussels CEN. 

The friction of road surfaces is often measured with a skid tester developed by the Road Research Laboratory17 and this has also been widely used on other surfaces and floors, including artificial sports surfaces. It is a pendulum device, the movement of which is arrested by the foot of the pendulum skidding on the surface to be measured. The skid resistance indicated can be approximately related to coefficient of friction by ... 

In 1971, a three-quarter mile surface overlay was placed in Oakville, Ontario using thirteen mix formulations. Skid resistance, wear, and permeability have been measured periodically to assess the suitability of sand-asphalt-sulfur mixes as surfacing materials. 

The noise generated from moving vehicles on open-textured surfaces, similar to PA, has been found to be reduced when compared with conventional surfacing materials of the same macro-texture and skid resistance coefficient. The reduction measured was 3 to 4 dB(A), when the pavement surface was dry, and 7 to 8 dB(A), when the surface was wet (Nelson and Ross 1981). Similar results were also found by the Belgium Road Research Centre (Decoene 1989) and by Phillips et al. (1995). At a later study, resurfacing an old concrete pavement with PA led to wind-normalised reductions in noise exposure of the order of 4.5 to 6 dB(A) L/ io,i8h at villages approximately 0.5 km from the motorway (Baughan et al. 2002). 

Figure 16.5 Skid resistance on wet road surfaces (measured with smooth tyre). (From Sabey, B.E., The Road Surface Texture and the Change in Skidding Resistance with Speed. Ministry of Transport, Road Research Laboratory, Report LR 20. Harmondsworth [Crowthorne], UK Transport Research Laboratory, 1966.)...

Apart from the braking system (locked wheel or partially locked [fixed slip ratio]), other factors influence the skid resistance measurements. These factors are (a) the speed of the device during measurements, (b) the tyre type of test wheel (the smooth type is the most common, or ribbed), (c) the load applied on the test wheel, (d) the amount of water applied on the surface (water film created) before the measurement and (e) the temperature of the air, tyre and pavement. 

The operational procedure for determining the skid resistance of a pavement surface by SCRIM or other similar SFC measuring devices is described and should comply with the CEN technical specification CEN/TS 15901-6 (2009). 

The skid resistance of the pavement surface may be measured by a considerably great number of devices on the basis of different principles. This fact renders the direct comparison of the results almost impossible. 

ASTM E 2340/E 2340M. 2011. Standard test method for measuring the skid resistance of pavements and other trafficked surfaces using a continuous reading, fixed-slip technique. West Conshohocken, PA ASTM International. 

CEN/TS 15901-8. 2009. Road and airfield surface characteristics - Part 8 Procedure for determining the skid resistance of a pavement surface by measurement of the sideway-force coefficient (SFCD) SKM. Brussels CEN. 

The Mu-meter is a trailer towed by a vehicle. The tester measures the side force friction of pavement. The results are expressed as Mu numbers. Skid resistance of paved surfaces is measured by a tester developed by North Carolina State University. This tester is a pendulum tester using a smooth rubber tire. The friction between the tire and the specimen is measured from the energy lost in the pendulum. A standard specification for a smooth tire is covered in a separate standard. ... 

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