Walkway Surfaces Research Articles

Slip Resistance Evaluation of 10 Indoor Floor Surfaces

Slip and fall injuries and fatalities continue to be a significant problem at work and in the community. Water is the most common contaminant that reduces traction on floors and other walkway surfaces resulting in a slip and fall event. This project investigated 10 common flooring surfaces to assess their slip resistance when dry vs wet and coated vs uncoated. Investigators used the English XL Variable Incidence Tribometer to measure slip resistance under all conditions. Results revealed a significant (p - value < 0.05) loss of slip resistance when wet vs dry. Investigators also found significant (p - value < 0.05) increases in traction when using a coating under wet conditions. Researchers support the use of coatings for floors and walkway surfaces that increase traction and reduce the chances of slip and fall events under all conditions.

Contaminant film thickness affects walkway friction measurements.

Walkway tribometers are used to measure available friction for evaluating walkway safety and pedestrian slip risk. Numerous variables can affect tribometer measurements, including the type and distribution of contaminants on the surface. Here, we quantified the effect of application method on contaminant film thickness, and the effect of film thickness on tribometer measurements on the four reference walkway surfaces used in ASTM F2508-16e. Distilled water, 0.05% sodium lauryl sulfate (SLS) solution, and 0.04% Triton X-100 solution were poured, squirted, and sprayed onto the surfaces to quantify their naturally occurring film thicknesses. These application methods had a significant effect on the resulting film thickness (p < 0.038), with the pour method consistently generating the thickest films and the spray method generating the thinnest films. We then quantified the effect of film thickness for the three contaminants (thickness range 0.3–3.3 mm) on the friction measurements of three common tribometers (Mark IIIB, English XL, and BOT 3000E) on each reference surface. A separate ANOVA was used for each of the 3 × 4 × 3 = 36 combinations of tribometer, surface, and contaminant. Friction measured with the Mark IIIB decreased with increasing film thickness on one surface across all three contaminants and on a second surface with the SLS contaminant. Friction measured with the BOT 3000E was sensitive to film thickness on two surfaces with water and one surface with Triton. The XL was unaffected by contaminant film thickness. Overall, despite significant differences in film thickness with contaminant application method, friction measurements were either insensitive to film thickness or varied only a small amount in all cases except for the Mark IIIB on the roughest surface. Film thickness did not alter the relative slip resistance of the four ASTM F2508 reference surfaces.

Human Slip Assessment of Candidate Reference Surfaces for Walkway Tribometer Validation: An Update to Standard ASTM F2508

Previous studies have reported on the concept of using human subjects to rank and differentiate walkway surfaces that vary in slipperiness. Surfaces identified as having different levels of slipperiness, based on the outcomes of human subject walking trials, are then used to validate tribometer slip resistance measurements. This concept was adopted in the development of ASTM F2508-11, Standard Practice for Validation and Calibration of Walkway Tribometers Using Reference Surfaces. Because of a depleting supply of the reference surfaces cited by ASTM F2508, new reference surfaces are needed. In this study, our objective was to assess new candidate reference surfaces to update the ASTM F2508-16, Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces. One hundred and forty-eight human subjects walked across four ceramic-based tiles (E, F, G, and H) under contaminated conditions. Our results revealed that, consistent with our prior studies, human subjects were able to rank and differentiate surfaces according to slipperiness. Moreover, the surfaces evaluated in this study demonstrate characteristics that make them suitable replacements for the ASTM F2508 reference surfaces. Based on our findings, we recommend that ASTM F2508 be updated using surfaces E, F, and G and that surface G be considered a candidate to establish a slip resistance threshold for walking.

Quantifying the uncertainty in tribometer measurements on walkway surfaces

Properly estimating and reporting the uncertainty of walkway surface friction is key to ensuring pedestrian safety. Here we quantified the amount and sources of uncertainty in friction measurements by having four users of four units of each of two walkway tribometer models (Slip-Test Mark IIIB, English XL) perform 12 measurements on four samples of four different surfaces that ranged from slippery to slip-resistant. We found that 51–82% of the total variance in the measurements was explained by the user, unit, sample and a user–unit interaction, which means that the variance a single user calculates from their own data does not capture most of the uncertainty in their measurements. Based on these data, the minimum uncertainty associated with the mean of a user’s measurements is ±0.064 (Mark IIIB) and ±0.072 (XL) to be 95% confident that their mean captures a surface’s available friction. Practitioner Summary: Walkway surface friction measurements are less accurate than they appear. Based on an experiment quantifying the amount and sources of uncertainty in surface friction measurements using two common tribometers, we quantified and report the minimum uncertainty that users can assign to their walkway surface friction measurements. Abbreviations: ANOVA: analysis of variance; ANSI: American National Standards Institute; CI: confidence interval; E: east; ILS: interlaboratory study; ISO: International Standards Organization; JCGM: joint committee for guides in metrology; N: north; S: south; SBR: styrene-butadiene rubber; SD: standard deviation; TR: test result; W: west

Investigation and Interpretation of Flooring Wear Development for Pedestrian Slip Resistance Assessments

ABSTRACTSurface conditions of pedestrian footpaths and walkways continually change throughout their services. Many causes may contribute to the variation of surface qualities, but a decline of slip resistance functioning is a critical problem for the pedestrian safety of walkway surfaces. Despite the importance of flooring wear issue, their ensured operations and influences on slip resistance performance against pedestrian falls have not been systematically investigated. The present study aims to understand wear progress of floor surfaces, investigate the mechanism of surface changes due to wear advances, and recognize their impacts on slip resistance operations. To measure traction properties and characterize wear behaviors of walkway surfaces, slip resistance tests were operated among three different types of floor specimens with a similar range of topographic characteristics and two dissimilar shoes. Wear formations and developments of the floor specimens were comprehensively assessed by a combination of numerical and microscopic investigations. The test outcomes evidently presented that the initial surface finishes of floor specimens were extensively modified by direct (straight move) and indirect wear processes (reverse and joint moves) and significantly affected slip resistance performance. The idea explored in this study may help to uncover valuable information for better understanding of the complex nature of slip resistance properties amongst the shoes, floors, and environments and have possible applications for the safety design improvements of pedestrian floors and floor coverings.

The science behind codes and standards for safe pedestrian walkways: Lighting and visual cues

BackgroundWalkway codes and standards are created through consensus by committees based on a number of factors, including historical precedence, common practice, cost, and, sometimes, empirical data. The authors maintain that codes and standards that can have an impact on human safety and welfare should give consideration in their formulation to the results of pertinent scientific research. PurposeThis article extends a companion one in examining many elements of common walkway codes and standards related specifically to lighting, warnings and markings. It indicates which elements are based on or supported by empirical data; and which elements could benefit from additional scientific research. Practical applicationsThis article identifies areas in which additional research leading toward scientific based codes and standards may be beneficial in enhancing the safety of pedestrian walkway surfaces.

Validation of Walkway Tribometers: Establishing a Reference Standard*

Tribometers are mechanical devices used to measure walkway coefficient of friction (COF) for the purpose of assessing slip risk. The purpose of this study was to define a tribometer reference standard and use it to assess the performance of various tribometers. Eighty subjects were randomly assigned to walk across one of four wet walkway surfaces (polished black granite, porcelain, vinyl composition tile, and ceramic tile) to establish the relative slipperiness of each surface. Eleven tribometers were subsequently used to measure and rank the COF of all four surfaces. Our results revealed that only four of the 11 tribometers (Wessex pendulum, Sigler pendulum, Mark II, and Mark III) met our compliance criteria by both correctly ranking all four surfaces and differentiating between surfaces of varying degrees of slipperiness. Our protocol demonstrates that human gait-based measures of slipperiness can be used to create reference standards against which tribometer measurements can be validated.

Forensic Engineering Use Of Walkway Traction Testing

Pedestrian Fall Events Are Frequently Linked To Slippery Walkway Surfaces. Friction Is The Measured Quantity At Issue In Traction Testing Which Has Been Conducted Using Various Devices For Over 80 Years. The Various Available Devices (Called Tribometers) Each Have Their Advocates, Resulting In A Certain Amount Of Controversy. Robust Analysis Of Walkway Traction Requires An Understanding Of Individual Tribometer Characteristics And Knowledge Of Potential Limitations In The Ability To Test Certain Surfaces &amp; Contaminants. It Is Also Necessary To Understand The Status Of Relevant Traction Testing Standards And To Be Familiar With Current Research Which Links Tribometer And Human Subject Testing To Provide Required Friction Values For Safe Pedestrian Ambulation.

Effect of Sand on the Slipperiness of Ice

Ice on walkway surfaces increases the chance that a pedestrian will slip and fall. Sand in the amount of 2.2 lb/100 ft2(10.8 kg/100 m2) increases slip resistance to about 0.5, the commonly accepted minimum slip resistance for a flat, straight walking surface. Ice covered with a layer of water has about the same level of slip resistance but could be more dangerous since the ice may not be perceived.

Repeatability and Bias of Two Walkway Safety Tribometers

Abstract Falls resulting from slips on walkway surfaces are a significant source of injury in society. To measure friction between the floor and the shoe, various types of tribometers and ASTM standards have been developed to assess walkway slip-resistance with the goal of improving pedestrian safety. The purpose of this study was to determine the repeatability and bias of the PIAST and VIT tribometers under both dry and wet conditions. Both devices were tested on an AMTI force platform over a wide range of angles. Bias was assessed by comparing the tribometer slip resistance reading to the actual Fx/Fz ratio measured by the force plate, while reliability was established by evaluating the ability of the tribometers to reproduce Fx, Fz, and the Fx/Fz ratio. Both tribometers demonstrated high degrees of bias and repeatability under both wet and dry conditions; however, each measured different slip-resistance values for the same surface. Further study should be directed at establishing which tribometer best simulates initial foot contact during gait with respect to measuring slip resistance.

Required Coefficient of Friction Versus Walking Speed: Potential Influences of Footwear and Walkway Surfaces

Abstract This paper presents data analysis for a representative subject from a pilot study where subjects walked at increasing speeds across a force plate in shoes with the top-piece/outsoles replaced by a variety of test materials, including test-foot materials commonly used in walkway-safety tribometry. The goal of this data analysis was to develop a methodology that can by used in a multi-subject experiment that combines force-plate and video data. More specifically, the objectives were: • To determine how force-plate assessment of required friction for subjects walking in shoes having soles and heels of various shoe-bottom or tribometric reference materials compares to tribometric testing of available friction using similar test-foot materials. • To explore the relationship between μr and walking speed as influenced by specific footwear and walkway surfaces. • To develop hypotheses to guide further data analysis and research. The force plate was covered with polypropylene, a substance expected to cause slipping with some of the test materials. The walking speeds ranged from moderate to as fast as the subject could walk. Required coefficient of friction μr was calculated from force-plate data. Average available coefficient of friction ¯μa was measured using a portable articulated strut tribometer with the test materials used as test feet. Computerized capture of sequential screens from time-coded videotape recordings of data stored on magneto-optical discs was used to visually assess the kinematics of walking and slipping. Observed slipping was studied in relation to the ratio of μr/¯μa. Profiles of μr versus time during stance were examined relative to top-piece/outsole materials and walking speed. Peak μr at heel contact versus walking speed was evaluated. Positive correlation was seen for certain test materials, while negative correlation was seen with others. The authors hypothesize that biomechanical adaptations of the subject to the footwear/floor-surface combinations account for observed differences. The paper discusses practical problems confounding use of the ratio μr/¯μa as a predictor of slip probability.

International Symposium on Slip Resistance: The Interface of Man, Footwear, and Walking Surfaces

Abstract The first four papers in this issue were presented at the International Symposium on Slip Resistance: The Interaction of Man, Footwear, and Walking Surfaces, held 30–31 October 1995 at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD. Sponsored by Committee D 21 on Polishes and Subcommittee D 21.06 on Slip Resistance, this symposium represents the culmination of research initiated in the 1950s to determine the coefficient of friction of polished walkway surfaces. Extensive laboratory and field studies of methods and apparatus led to the development of the ASTM Test Method for Static Coefficient of Friction of Polish-Coated Floor Surfaces as Measured by the James Machine.

On Threshold Values That Separate Pedestrian Walkways That Are Slip Resistant from Those That Are Not

Abstract Pedestrian accidents generate significant direct, morbidity and mortality costs. Slip accidents are generally a result of a number of factors. One factor that has received considerable attention is the walkway-surface slipperiness. It is desirable to be able to isolate, to the extent possible, the contribution of the walkway surface to slipperiness. It has been the practice of those involved in evaluating walkway slip resistance to test the floor against a standard test foot under specified conditions and compare the results of that testing against a threshold. Those walkway surfaces that produce a friction coefficient above the threshold are considered acceptable. Past and present tests and associated thresholds are discussed. Abuse issues are discussed. It is recommended that field tests measure the available friction with a tribometer capable of correctly characterizing the friction model experienced by the pedestrian and compare that against a utilized friction threshold, determined by normative or force-plate means, for activities foreseeable in the area where a fall occurs.

Measurement of the slipperiness of walkway surfaces

Measurement of the slipperiness of walkway surfaces