How the pendulum works, and what a PTV means.

The pendulum — or "TRL pendulum" — is a portable instrument that swings a weighted arm tipped with a rubber slider across the floor. The grip of the surface saps the swing of momentum, and that loss is read on the dial as a Pendulum Test Value (PTV). The higher the PTV, the more friction the floor offers and the safer it is.

Why this test

It is the method set out in BS 7976-2 and BS EN 16165 and the one the HSE names as its preferred approach for assessing both new and existing floors and for investigating accidents. By reproducing a heel strike it reflects real slipping far better than how a floor feels underfoot.

Wet, dry and three directions

We test each area in three directions and, crucially, in the wet — because that's when floors turn dangerous. Recording along, across and diagonally to the line of travel captures any directional grain or wear.

Two slider rubbers

For shod areas we use the Slider 96 (4S); for barefoot areas such as pool surrounds and changing rooms we use the Slider 55. Both can be used on heavily profiled surfaces.

Surface microroughness

On water-wetted floors we can add a surface microroughness reading (in microns), which the HSE recognises as a useful companion measurement to the pendulum.