Friction Tests on Contaminated Surfaces

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brian
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Friction Tests on Contaminated Surfaces

Post by brian »

2006 TRL Limited report on friction tests on contaminated surfaces: “Friction Tests on Contaminated Road Surfaces”, Lambourn & Viner.
The following are portions of the various sections:
Executive Summary:
  • The presence of containments in the tyre/road interface can reduce the friction generated between the tyre and the road. The sudden reduction in this friction experienced by the driver of a vehicle who traverses an area of road surface subject to contamination could potentially contribute to a loss of control of the vehicle and thus could pose a serious hazard. The objective of the study was to test various selected contaminants to identify the contaminants which, on a typical road surface, cause the greatest loss of friction and to provide guidance as to the importance of this effect.
Summary:
  • The results show that, for the skid cars, the reduction in friction observed with the contaminants, as compared to the dry and wet conditions, is clear but modest. The lowest figures, of 0.41 for oil on asphalt and 0.44 for diesel on the concrete, are lower than the corresponding measurements on these surfaces when wet, but comparable with figures which may be found on other road surfaces that are wet. These figures may be surprising in view of the commonly held belief that spilt diesel fuel will make a road dangerously slippery, and that engine oil might make it more slippery still.
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    Unlike the results with the cars, the friction coefficients recorded with the PFT(Pavement Friction tester, see below) in the presence of contaminants are below the range of values expected from road surfaces in wet conditions and in the worst case, are virtually zero. The comparison of the PFT results with those from the skid cards provides an indication of the relative influence of tyre condition and surface texture.
CONCLUSIONS:
The following are some of the conclusions drawn from this study:
  1. For small or medium sized cars with tyres in good condition, skidding on a surface with good skid resistance and moderate or high texture depth, friction coefficients above 0.4 could be expected for all the contaminants tested, even when spread copiously or in a thick layer. This performance is no worse than might be expected on many road surfaces when wet.
  2. The tyre tread is critically important to delivering this performance and, with s11100th tyres , friction coefficients of practically zero can be observed in some circumstances. This worstcase scenario may apply even when the underlying surface is highly skid resistant and with a good texture depth.
  3. Other than the tyre tread, the important parameters influencing the result seem to be the viscosity of the liquid contaminants followed by the surface texture (with the engine oil – the most viscous contaminant - a virtually zero friction coefficient was recorded on a surface with good underlying surface texture).
  4. The performance of the proprietary absorbent material in clearing up the contamination was superior to that of sand.
The main implication of this work for highway authorities is that, given the worst-case scenario it is clearly important to avoid contamination or clear it up as quickly and effectively as possible. For areas where contamination may occur regularly, such as agricultural accesses or entrances to refuse disposal facilities, it is recommended that a regime of regular inspection and decontamination of the road surface be enforced. Where spillage of liquid contaminants is involved, it is recommended that a proprietary absorbent product is used to remove the contamination in preference to the use of sand for this purpose. Consideration should also be given to whether the risks to road users as a result of the presence of contamination could be mitigated by the use of warning signs or speed restriction

PFT=Pavement Friction Tester which is a locked-wheel friction tester consisting of a towing vehicle and purpose built test trailer fitted, for this study, with ASTM standard smooth tyres (ASTM E524-88). This equipment is common in the United States and is used in England by the Highways Agency for research.
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MSI
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Re: Friction Tests on Contaminated Surfaces

Post by MSI »

Some recent posts to INCR on the topic included some additional references for research on the topic:
  • Consider joining INCR as its a great resource for information, and thanks to the folks who posted up on these and other topics...
    I don't identify them as members are not supposed to name names so posting simply the useful information
    THANK YOU INCR!!

Some references and information: another posting included:
  • I would suggest that you consider:
    • Roodt L. D. V., ‘Skid resistance of Roads Contaminated with Gravel’ 32nd Southern African Transport Conference, July 2013, Pretoria, South Africa, which references:
      1. Lea J. D. and Jones, D. J., ‘Initial Findings on Skid Resistance of Unpaved Roads’ Transportation Research Record: Journal of the Transportation Research Board Issue Number: 2016: Transportation Research Board
      2. Wahl J., ‘Determining the tyre-road coefficient of friction of polluted road surfaces’ Unpublished final year project report, Stellenbosch University, Stellenbosch.

      Roodt presented data from:
      • Lea and Jones : "Unpaved roads have a dynamic surface, which can make it difficult to predict the skid resistance of a section for use in geometric design and gravel selection and to schedule maintenance. This investigation showed that there are three mechanisms for skidding on unpaved roads: intersurface friction, sliding on a thin layer of loose material, and ploughing through a thick layer of loose material. The main surface and material properties affecting skid resistance are the stoniness severity and extent, the severity and extent of raveling, and the amount of loose material in the 0.850-mm to 2.00-mm range on the surface. The range of coefficients of friction for unpaved roads is from 0.40 to 0.85, with the lower value being conservative."
        • The average skid deceleration reported by Lea and Jones on dry gravel road from:
          • 50km/h was 0.67 from 16 tests;
          • 80 km/h 0.62 from 7 tests.
      • Wahl: skid deceleration tests were conducted using a Mazda Rustler light delivery van without Anti-lock Brake System (ABS).
        Deceleration testing was conducted from 60km/h and commenced 5m before an area of sand (5mm and smaller) on a surfaced test road.
        The results from 10 tests showed an average skid resistance of 0.39 with a range of 0.36 to 0.44 and standard deviation of 0.03.
        • The average skid deceleration for an ABS equipped Chrysler Voyager on a:
          • Re-gravelled unsealed road at 0.56 (with the range of 0.53 to 0.63).
          • 13.2mm gravel on a surfaced road was 0.39 (with the range of 0.37 to 0.41).
          • 6.7mm gravel on a surfaced road was 0.45 (with the range of 0.44 to 0.47).
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Re: Friction Tests on Contaminated Surfaces

Post by MSI »

Recently on INCR another reference cited:

The effect of contaminant on skid resistance of pavement surface
A S Lubis, Z A Muis and E M Gultom
Abstract
  • Skid resistance of the pavement surface is the force generated by the movement of the wheels of the vehicle on the surface of the pavement. Contaminants are materials that cover the surface of the pavement affecting the skid resistance of the pavement surface. The contaminant acts as a coating interface or direct contact of the pavement surface with the wheels of the vehicle which can cause adverse effects, such as the decreasing value of skid resistance of the pavement surface. This study aims to analyze the effect of some types of contaminants on skid resistance of pavement surfaces. The contaminants that used in this study were water, sand, salt, and lubricating oil. The study was conducted by direct testing on two types of pavement: flexible pavement and rigid pavement. The measurements of the skid resistance were made using the British Pendulum Tester with British Pendulum Number for two conditions: before and after the pavement surface was covered with contaminants. The results showed that there was a contaminant effect on skid resistance of pavement surface. Skid resistance of pavement surfaces decreased after the contaminants were covered in water, sand, salt, and lubricant by 20.1%, 22.8%, 37.1% and 50.5% respectively
Conclusion
  • Based on the results of the research there are some conclusions as follows:
    1. Based on minimum skid resistance value, the skid resistance value on flexible and rigid pavement before exposure to contaminants were still adequate, but after exposure to contaminants were inadequate; (
    2. There was an effect on the skid resistance value on the pavement surface with water, sand, salt, and lubricating oil as contaminant on the surface of flexible and rigid pavements;
    3. The contaminants that gave the effect of the skid resistance decrease value from the smallest to the greatest were water, sand, salt, and lubricating oil.
Lubis Table 3.png
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Lubis Table 4.png
Lubis Table 4.png (25.38 KiB) Viewed 124 times
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