This paper discusses the disparity of the results obtained for the measurement of slip resistance, and, in particular, the difference between results obtained by using two portable devices. The pendulum skid resistance tester, designed by the Transport and Road Research Laboratory, was and still is used to measure the skid resistance of road surfaces, but it has also been applied to pedestrian pavements. The more recently invented tortus gives a direct reading of the lateral force required to drag a loaded slider across a floor. The tortus generally gives lower values for the coefficient of friction in dry conditions, while the pendulum usually gives lower values in wet conditions. The design of the two machines is totally different. This paper gives some mathematical results about the behaviour of the devices, and its appendices explain their design and operating principles, state the basic assumptions used about coefficient of friction, and present the results of comparative tests. The following conclusions are reached: (1) the pendulum appears to estimate pedestrian slip resistance accurately in wet slip conditions, and it can easily be adapted to assess it accurately in dry conditions; (2) the Greater London Council's findings of correlations between pendulum readings and the slip resistance of surfaces, as estimated from their accident history, are not surprising; (3) in wet conditions, the tortus generates a much thinner hydrodynamic film, thus greatly overestimates the coefficient of friction for the majority of surfaces that are potentially dangerous to pedestrians. (TRRL)

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    Scientific and Technical Press Limited

    Chilberton House, Doods Road
    Reigate, Surrey,   England 
  • Publication Date: 1988-9

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  • Accession Number: 00492759
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Mar 31 1990 12:00AM