Yes, a foot. And it's not a fine test, its wrong, but lets go with it. I have time
I'm not saying that any test is a 100% accurate real world simulation, but the PTV is far closer to a simulation, than a guy in safety boots on a tilting ramp covered in oil. But on the other hand if you like taking showers in oil, in boots with your falls in the tray being at a 30 degree slope, you crack on.
Take a pool surround for example. Just wet, not covered in motor oil and you are not likely to be wearing rubber soled safety boots and its not tilted. Its flat. Its no comparison! How can you be telling me an R rating has any bearing on how slippery that floor will be in bare feet with just water?
The Munro PTV tester has a weighted arm and a selection of slider pads made of different grades of rubber that have been designed to simulate a walking leg, with a variety of shoe soles (one of these will be graded by the HSE as "sensible footwear") and bare feet. The pendulum swings and is calibrated to hit the tile slowing down and swing back up to a scale, giving the result in PTV, a scale that has been invented purely for slip risk assessment purposes. This can be anywhere from zero upwards but the HSE following many tests have deemed that 36+ is the "safe line" and anything less will be moderate to dangerous. and also, don't forget, two test results, one dry test, one wet test so easier to see a suitability for a particular condition.
Now, taking your uneven floor as example, which way are you walking? up the slope or down the slope? is it slanting down from the right or the left, because obviously we know that walking up a slope, because of the angle of impact is going to be more resistant in itself than the angle you'll be impacting at if it was sloping away???? Maybe the german man should also stand sideways on the ramp too, just in case.
Sorry if that was sarcastic, no offence intended, but you see my point. R Ratings are useless. It doesn't make sense. The initial PTV is calculated on a flat surface for initial tests to give the result, but the tester does not define the angle the tile will be laid at, thats down to the end user, and the angle will slightly alter the slip potential, but at least they had something better to go on when picking the tile out. The pendulum tester is portable and can taken out on site so any floor can be also tested after fixing, at any angle if there are concerns. They will do 3 directional tests and take the average value to give the on-site PTV.
Also at the end of the day, if there is a claim in court for an injury from an accident or slip, the court will rule the floor as safe or not safe, based on the HSE requirements not the R ratings.
Need a cup of tea now
(Edit. If you read this before I edited it, I said, "Standing Still". This was incorrect and although they are restricted, they are only able to step within a short sample area....... still wearing grippy boots though, and still continuously pouring oil on it, meaning it is not representative of end use and as such is a poor indicator of slip resistance.)
