Microtexture is the fine-scale roughness of the individual aggregate particles, felt as harshness if you run a hand over the stone. It provides grip at low speeds and is what the pendulum tester principally measures. Macrotexture is the coarser void structure between the particles, which lets water escape from under a tyre and therefore controls wet grip at higher speeds. Both are needed: a polished but open-textured surface and a rough but tight-textured one each fail differently.

A weighted arm carrying a rubber slider is released from a fixed height and swings across a wetted section of the surface. Friction between slider and surface retards the swing, and how far the arm rises afterwards gives the pendulum test value. The method is defined in EN 13036-4. It is portable, needs no vehicle, and is used both on roads and on pedestrian floors, which makes it the most widely available friction instrument.

It measures macrotexture depth. A known volume of graded sand or glass beads is spread into a circular patch on the surface, filling the voids until level with the peaks of the aggregate; the patch diameter gives the mean texture depth. It is defined in EN 13036-1, needs no instrumentation beyond the material and a spreading tool, and is the standard check that a new surfacing has the texture depth its specification requires.

When the question is about a route or a network rather than a location. Spot tests are labour-intensive, require traffic management and sample only where you place them, so a defect between test points is missed. Sideway-force, locked-wheel and grip-tester systems measure continuously at traffic speed and produce a profile of the whole length, which is what network condition surveys and routine safety monitoring require.

The pendulum tester, yes, and it is the standard instrument for pedestrian slip resistance in many markets, used on floors, ramps, stair treads and wet areas with a different slider rubber from the road version. The vehicle-mounted systems and, in practice, the sand patch method are specific to trafficked pavements. Check which slider and which procedure the relevant flooring standard calls for, since the values are not interchangeable with road figures.

On a network, at the interval set by the road authority's safety inspection regime, with high-risk sites such as bend approaches, junctions and pedestrian crossings monitored more frequently. Outside routine monitoring, test after resurfacing as acceptance, when investigating a collision cluster, and where a surface is visibly polishing. Aggregate polishes progressively under traffic, so friction falls gradually and is not apparent from a visual inspection.

Surface wetting, temperature, slider condition and the exact test position. Pendulum results are temperature-sensitive and are corrected accordingly, the slider rubber wears and must be conditioned and replaced on schedule, and the surface must be wetted consistently. Because texture varies over short distances, several swings are taken at a location and averaged. Calibration of the instrument, including the slider, is what makes results comparable between operators and over time.