Slips and trips are the leading cause of workplace injuries, accounting for over a third of all major injuries and more than 40% of reported injuries to the public. According to HSE statistics, the majority of these incidents are slips, which typically occur when floor surfaces are contaminated with substances like water or talc.
Slip testing and the surface roughness measurements offer a straightforward way to assess slipperiness in water-contaminated conditions. These measurements can also track changes in floor surface characteristics, such as wear. Research has demonstrated that the Rz parameter is an effective predictor of slipperiness across various common materials. Rz represents the total surface roughness, calculated as the average of multiple peak-to-valley measurements.
Where only surface roughness data is available, it should be used in conjunction with the Slips Assessment Tool (SAT) detailed below.
Scientists at HSL have demonstrated that Rz roughness parameter, the roughness of floor surfaces, is a strong indicator of their slipperiness, particularly under wet conditions where most slips occur. The ‘Rz Surface Microroughness’ measure has proven to be a reliable metric for assessing slipperiness. Rz roughness is calculated by repeatedly measuring the vertical distance between the highest peak and the lowest valley on a small scale within the test area. This roughness is then expressed in microns, which are millionths of a meter.
Measuring Rz with a handheld meter is both quick and easy. However, roughness meters are not suitable for use on carpeted, uneven, or extremely rough surfaces.