The "Traction Index" Report

Title: ''The Traction Index - A New Method for Measuring the Relative Slip Resistance of Footwear and Flooring''

Objective: To establish a slip resistance measuring technique which eliminates the variability of the leather and rubber sensor pads when measuring the SCOF of flooring and utilizes standard test surfaces when measuring the SCOF of both footwear materials and complete footwear and footwear sole and heel materials.

Method: Standard test surfaces are used for standardizing the leather and rubber sensors in order to calculate both the leather and rubber correction factors when testing leather dry and a synthetic rubber (Monarch EVA) both dry and wet. The ''standard SCOF'' of leather is marked on the back of a polypropylene leather (and synthetic leather) test panel. The ''standard SCOF" of Monarch EVA, both dry and wet (distilled water), is marked on the back of the ASTM C1028 ceramic calibration tile. These same surfaces are used to test complete footwear soles and heels and footwear materials.

The complete shoe heel and sole, depending on whether they are leather, synthetic leather or rubber, is placed alternately on the polypropylene and ceramic tile test surfaces. A 10-lb. weight is placed above the heel or sole with a string loop, taped to the edge of the sole, which is hooked to the force gage. A horizontal force is applied to the string until the sole or heel starts to slip. This force, divided by the weight of the shoe plus the 10-lb. weight, is the SCOF of the heel or sole. This SCOF, divided by the ''standard scof" marked on the test panels, is the ''Traction Index'' of the heel or sole. This compares the footwear sole and heel materials to "standard leather" and "standard rubber (EVA)".

This method is novel because the slip resistance of any floor or floor coating, using leather and rubber sensors, can be compared to the minimum SCOF required for a slip-resistant floor by determining the ratio of the measured SCOF to the minimum required SCOF. In this manner a ''Traction Index'' is calculated which provides a direct indication of the slip resistance of the floor to ''standard leather'' dry and ''standard rubber'' dry and wet. The leather sensor is tested dry against polypropylene and the rubber sensor (Monarch EVA) is tested dry and wet (distilled water) against the ASTM C1028 ceramic calibration tile in order to determine leather and rubber correction factors for correcting the average SCOF of 8 onsite tests to "standard leather" and "standard rubber (EVA)".

These same surfaces are then used to measure the traction index of the heels and soles of complete footwear. The footwear heel and sole traction indices are the ratio of the measured SCOF to the standard SCOF of ''standard leather'' and ''standard rubber'' marked on the back of the two test panels as previously stated.

This measuring technique permits forensic engineers, who investigate slip/fall accidents, to determine the traction index of both the floor at the accident site and the victim's footwear. This test method permits both flooring and footwear manufacturers to rate their products based on the ''Traction Index''.

The flooring "Traction Index" finally solves the problem of accurately measuring the slip resistance of flooring, both dry and wet, with standardized leather and rubber sensors. Valid measurements cannot be obtained without standardizing the sensors.

The footwear (sole & heel) "Traction Index" finally establishes standard test surfaces for measuring leather type footwear materials dry and rubber type footwear materials dry and wet.

This method makes every other slip resistance test method obsolete i.e. ASTM flooring and footwear test methods specified in VOSI V41.23X and VOSI V41.23Y respectively.

Donald Meserlian, P.E., 
VOSI Chairman Voices of Safety International (VOSI) 

Voices of Safety International (VOSI) - 1998 - 2018
Last Updated: 2001-03-28