SlipAlert Vs Pendulum Testing

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Pendulum Skid Tester

The Pendulum was originally designed to test the slip resistance of floors. However, it was not until the UK Transport Research Laboratory found it a useful machine for testing roads that it first found fame. Later research proved that it is a very useful measure of slip resistance of floors, and the Pendulum is now asserting itself as the gold standard for measuring dynamic slip resistance of floors.

The TRL Pendulum is also known as Pendulum Skid Tester because it is also used to test road slip risk. Values or PTV 45 or more will be required and some roads need PTV 65 or more.

Known as

• British Pendulum

• Transport Research Laboratory Pendulum

• Pendulum Skid Tester

• Sigler Pendulum test

• The Pendulum is manufactured by two British companies:

• Wessex Engineering

• Munroe Group

Pendulum Calibration and use

Dr Malcolm Bailey former secretary of the UKSRG is one of the most experienced Pendulum users in the world. He often comments that to use the Pendulum effectively in different flooring situations takes years of experience.

TRRL Pendulum Test Values and slip risk

PTV of 36 is equivalent to a slip risk of 1:1million according to estimates done in 1950’s in UK. Some prefer PTV 40 for safety where people may be walking fast, running, turning or twisting. SlipAlert measures better than STV of 130 should be considered safe.

PTV of 24 is considered the absolute minimum value for public flooring equates to COF 0.24 or STV or 173. This equates to approximately 1:20 slip risk. Far too high a risk in a public building with many pedestrians.

The SlipAlert was designed to correlate with a slipping pedestrian. The HSE recognise SlipAlert as an accurate portable slip assessment tool. It has a very high correlation with the Pendulum, the de facto industry standard.

The Pendulum formerly appeared in British Standard 7976 now BSEN16165, SlipAlert in British Standard 8204. Read the full HSE report. Since then, the HSE have growing evidence that SlipAlert is robust, practical and the best portable floor testing tool.

  • Contact us with your SlipAlert needs...

    Did you know?

    So far this year slips have cost society at least:



    of all accidents to the public are slips and trips.

  • “The extended testing of SlipAlert showed a good correlation with the Pendulum test…”

    “SlipAlert should be regarded as a good indication of available friction, lending itself to risk assessment, monitoring of floor surfaces and evaluating & monitoring cleaning regimes”

    “SlipAlert tends to give fail-safe readings”


    SlipAlert Pendulum Correlation

    SlipAlert test results speak for themselves. There is a very high correlation between SlipAlert and the Pendulum in both wet and dry conditions across a range of surfaces. The HSE in the UK now accept that SlipAlert is a very good way to test floors and that it consistently gives accurate results wet or dry.

    Each point of the graph corresponds to a measure of slip coefficient on a different surface as measured by SlipAlert and the Pendulum. The big advantage of SlipAlert is that it is portable, it works on both wet and dry surfaces and its so easy to use, anyone can do it. PTV 36 should be a safe floor for normal pedestrian walking. PTV 40 (co-efficient of friction 0.4) should be safe enough for running or turning.

    SlipAlert Strengths

    • “Easy to use”
    • “Recognises contamination”
    • “Visual”
    • “Portable”
    • “Measures friction”
    • “Robust”
    SlipAlert FeaturesBenefits for you
    Quick and easySaves you time and more thorough. Floors can be tested in a trice and different areas of floor can be tested to check for wear or poor cleaning.
    Reliable test for all floorsSaves you money. Management information to prevent you buying poor flooring or poor cleaning products.
    Tests slip risk wet and dryEasy to manage slip risk on all floors in all conditions. Most slips occur on wet floors.
    Visual and intuitiveNo training for use, easy to see if floor is safe, easy to spot anomalies.
    Detects contaminationShows if your floors are being cleaned properly. Easy to detect risk from spills or polish or other contaminants.
    Detects changes to slip risk caused by wear.Helps you understand the effects that wear will have on slip resistance of your floors and plan for future.
    Comes complete with carry case, ramp and support to help you understand and manage slip risk.You and your team will quickly learn how to measure and manage slip risk and you can develop a floor safety regime to reduce slip accidents and reduce slip injuries.
    Test new floors, test changes, test the effectiveness of cleaning, test for wear, and test after slip incidents.Fast, effective testing. Inexpensive options to test yourself or using a local test service. Establish and maintain safe levels for every floor. Eliminate slip injuries.

    Designed for regular testing to stop slips & falls

    SlipAlert was designed specifically to be easy to use and give consistent results in wet and dry that match the Pendulum. It is designed for regular testing and designed to give you the management information you need to keep floors safer and stop people falling.

    What action to take to prevent slips

    There are often easy, low-cost actions that will improve floor safety and prevent slip accidents. It may be that you need to improve your cleaning regime or cleaning materials, or it may be that your floors require an occasional deep clean. Depending on the nature of your floors, we will be able to offer advice. 

    Easy Floor Testing

    Red, AmberGreen… floor safety indicator

    Use the handy SlipAlert graph to see if your floor is very safe, very dangerous, or if like most floors it will need monitoring to reduce slip risks.

    When / Where to test

    • Test new floors
    • Test the floor when it changes
    • Test when there is an accident or near miss
    • Test floors whenever there is an accident or near miss
    • Test floors when changed: polishing, coating, chemical spill etc
    • Test “at risk” floors every week and monitor the trends

    An “at risk” floor is one that has had recorded slip accidents, one that has been treated with anti-slip or a floor that has been tested and found to be less than perfect (STV of 130 or better).

    PTV and co-efficient of friction

    SlipAlert Results Graph 184x100mm Dec23
    With SlipAlert you can easily convert SlipAlert Test Values (STV) into PTV or co-efficient of friction values using the graph on your SlipAlert ramp (see above image). You will see that STV 130 corresponds to PTV of about 40 (co-efficient of Friction about 0.4) which is slip risk of approximately 1: 1 million and considered safe. STV of 173 equates to PTV of 20 (0.2 CoF) slip risk massively larger at 1:20. PTV and CoF align fairly well up to PTV 50 (CoF 0.5), but above this values most floors are safe enough.

    Coefficient of Friction (CoF)

    The coefficient of friction is defined as H/V, where H and V and the Horizontal and vertical forces acting when your shoe heel contacts the floor.

    Co-efficient of friction tests often fail to accurately reflect the slip risk for pedestrians because of hydrodynamic film theory and the effect of a barrier of water or other viscous material between your shoe heel and the floor surface.

    Most slip meters measure coefficient of friction but fail to account for the hydrodynamic sqieeze film effect and fail to account for the interaction between the shoe heel and the contaminant and the floor surface. Only SlipAlert and the Pendulum accurately simulate a real pedestrian slip.

    CoF values up to 0.4 match well with equivalent PTV 40. So, a CoF of 0.36 is considered safe for normal walking.

    Other testers and slip measurement machines

    • English Xl
    • GMG slip test
    • Tortus Tortus2 Tortus3
    • FSC2000, FSC 2000
    • American Slip Meter ASM825
    • BOT, BOT2000, BOT 2000 BOT3000 BOT 3000
    • Rz microroughness, and SAT Slips Assessment Tool
    • Sigler Pendulum Tester or TRL Pendulum skid tester
    • German Ramp test
    • The James Machine
    • Slip Guardian
    • Brungraber, Mk I, Mk 2

    Some will argue that slip test measures like the BOT-3000 are useful in court cases because they provide a credible measure of slip resistance and a printout of coefficient of friction of the floor. If you wish to contest evidence in a courtroom from the BOT-3000 or other slip testers such as the TORTUS, GMG, GSC200 then you should conduct a simple slip test on smooth tiled floors. Measure the slip risk of the dry floor, the wet floor, and the floor with a coating of grease or oil plus water. Many slip testers like the BOT-3000 will show the floor to be safer when wet than it is when dry. This is clearly counter to actual slip experience where most slip accidents occur on wet or contaminated floors.

    It is important to note that the HSE does not accept these tests as a valid method for assessing the slip resistance of floor surfaces as they provide inaccurate data in contaminated conditions.”

    Surtronic Meters won't measure slip risk

    Rz micro roughness is not a direct measure of slip risk, and cannot help you to monitor changes to the slip risk of your floors. Ask the HSE for the latest correlation between roughness and PTV. Roughness cannot detect change to slip risk caused by wear, contamination or other major causes of change to the slip risk of your floors.