Wen-Ruey Chang

Chang WR Falls Prevention, LLC

Research has shown that safety climate predicts safety outcomes in various occupational settings. One important component of safety climate is employees’ perceived priorities of safety in an organization relative to other operational demands (e.g., productivity or efficiency). The relationships between three dimensions of employee perceptions of sa...

Multiple sensing mechanisms could be used in forming responses to avoid slips, but previous studies, correlating only two parameters, revealed a limited picture of this complex system. In this study, the participants walked as fast as possible without a slip under 15 conditions of different degrees of slipperiness. The relationships among various r...

Kinematics at heel strike instant (HSI) has been used to quantify slip severity. However, methods to identify HSI remain ambiguous and have not been evaluated under slippery conditions. A glass force plate was used to observe the contact interface between shoe and floor under slippery conditions. HSIs identified from the video captured beneath the...

Portable ladders incidents remain a major cause of falls from heights. This study reported a field observation of environments, work conditions and safety behavior involving portable ladders and their correlations with self-reported safety performance. Seventy five professional installers of a company in the cable and other pay TV industry were obs...

Gait adaptation to employ different ways to avoid a potential slip is needed to continue walking safely on a new surface, especially when transitioning to a slippery surface. In this experiment, participants walked back and forth five times (trials) on surfaces with different degrees of slipperiness. The results show that trial 1 was significantly...

Occupational slips, trips and falls on the same level (STFL) result in substantial injuries worldwide. This paper summarises the state of science regarding STFL, outlining relevant aspects of epidemiology, biomechanics, psychophysics, tribology, organisational influences and injury prevention. This review reaffirms that STFL remain a major cause of...

Ladder inclined angle is a critical factor that could lead to a slip at the base of portable straight ladders, a major cause of falls from heights. Despite several methods established to help workers achieve the recommended 75.5° angle for ladder set-up, it remains unclear if these methods are used in practice. This study explored ladder set-up beh...

Forty participants, ages 18–45 years, rated perceived slipperiness before and after walking on five different floors under three different surface conditions. The before-ratings were taken as a proxy for visual cues to slipperiness, while after-ratings were taken as a proxy for somatosensory feedback received while walking on the surface. Before an...

Introduction: Although exercise and strength training have been shown to be protective against falls in older adults (aged 65 years and older), evidence for the role of leisure-time physical activity (LTPA) in the prevention of falls and resulting injuries in middle-aged adults (aged 45-64 years) is lacking. In the present study, we investigate th...

Heel strike instants are an important component of gait analyses, yet accurate detection can be difficult without a force plate. This paper presents two novel techniques for kinematic heel strike instant (kHSI) detection which examined maximal resultant horizontal heel displacement (HHD). Each of these HHD techniques calculates HHD from a selected...

Safety climate has previously been associated with increasing safe workplace behaviours and decreasing occupational injuries. This study seeks to understand the structural relationship between employees' perceptions of safety climate, performing a safety behaviour (ie, wearing slip-resistant shoes) and risk of slipping in the setting of limited-ser...

Perceived slipperiness rating (PSR) has been widely used to assess walkway safety. In this experiment, 29 participants were exposed to 5 floor types under dry, wet and glycerol conditions. The relationship between their PSR and objective measurements, including utilized coefficient of friction (UCOF), gait kinematics and available coefficient of fr...

Background/Objective Physical activity has been shown to be beneficial at improving health in some medical conditions and in preventing injury. Epidemiologic studies suggest that physical activity is one factor associated with a decreased risk for slips and falls in the older (≥65 years) adult population. While the risk of slips and falls is genera...

Several studies have indicated that slip-resistant shoes may have a positive effect on reducing the risk of slips and falls, a leading cause of injury at work. Few studies, however, have examined how duration of shoe usage affects their slip-resistance properties. This study examined the association between the duration of slip-resistant shoes usag...

Perceived slipperiness rating (PSR) has been widely used to assess walkway safety. In this experiment, 29 participants were exposed to 15 different floor conditions. The relationship between their perceived slipperiness rating and all other objective measurements, such as utilized coefficient of friction (UCOF), kinematics and available coefficient...

The maximum coefficient of friction that can be supported at the shoe and floor interface without a slip is usually called the available coefficient of friction (ACOF) for human locomotion. The probability of a slip could be estimated using a statistical model by comparing the ACOF with the required coefficient of friction (RCOF), assuming that bot...

The goal of this study was to examine the external validity of a 12-item generic safety climate scale for lone workers in order to evaluate the appropriateness of generalized use of the scale in the measurement of safety climate across various lone work settings. External validity evidence was established by investigating the measurement equivalenc...

This study examined data equivalency and loss to follow-up rates from Internet and interactive voice response (IVR) system surveys in a prospective-cohort study. 475 limited-service restaurant workers participating in the 12-week study were given a choice to report their weekly slipping experience by either IVR or Internet. Demographic differences,...

This paper presents an investigation on different slip probabilities for level straight walking obtained when comparing a given available coefficient of friction (ACOF) value with the stochastic distribution of the required coefficient of friction (RCOF). In an early study, data from both feet of 48 participants were pooled to construct a normal di...

Introduction: Occupational slips, trips and falls account for over 25% of injuries with days away from work in hospitals. A case follow-back study was conducted to better describe the circumstances experienced by hospital workers who had slipped, tripped or fallen (STF). Method: One hundred fifty-three health care workers, who reported a STF to t...

Background Telephonic interactive voice response (IVR) systems and Internet-based surveys have provided new methods of collecting longitudinal data for injury researchers. A choice of multiple survey modes has been shown to increase response rate. Different survey methods can lead to different responses to same questions. Objectives This study exam...

Objectives Falls are a leading cause of injury at work, and slipping is the predominant cause of falling. Prior research has suggested a modest correlation between objective measures (such as coefficient of friction, COF) and subjective measures of slipperiness (such as worker perceptions) in the workplace. However, the degree of association betwee...

Many studies have found management commitment to safety to be an important construct of safety climate. This study examined the association between supervisor and employee (shared and individual) perceptions of management commitment to safety and the rate of future injuries in limited-service restaurant workers. A total of 453 participants (34 supe...

The purpose of this study is to explore and examine, specific to the restaurant industry, two important constructs emerging from the safety climate literature: employee perceptions of safety training and management commitment to safety. Are these two separate constructs? Are there both individual- and shared group-level safety perceptions for these...

Unlabelled: This study investigated the stochastic distribution of the required coefficient of friction (RCOF) which is a critical element for estimating slip probability. Fifty participants walked under four walking conditions. The results of the Kolmogorov-Smirnov two-sample test indicate that 76% of the RCOF data showed a difference in distribu...

Unlabelled: The required coefficient of friction (RCOF) is an important predictor for slip incidents. Despite the wide use of the RCOF there is no standardised method for identifying the RCOF from ground reaction forces. This article presents a comparison of the outcomes from seven different methods, derived from those reported in the literature,...

The required coefficient of friction (RCOF) is one of the critical elements in determining whether a slip incident might occur. Most researchers, when measuring RCOF, do not differentiate between the two feet of the same participant under the same walking condition. Results from a recent study (Chang et al., 2010) indicated that the stochastic dist...

The available coefficient of friction (ACOF) for human locomotion is the maximum coefficient of friction that can be supported without a slip at the shoe and floor interface. A statistical model was introduced to estimate the probability of slip by comparing the ACOF with the required coefficient of friction, assuming that both coefficients have st...

An enhanced methodology to extract the required coefficient of friction (RCOF) value was used to investigate the effects of the transverse shear component of the ground reaction force (GRF) on the RCOF. The RCOF is an important indicator for slip incidents. However,the extraction of the RCOF from GRF is not standardized. The transverse shear force...

Slips and falls are a leading cause of injury at work. Several studies have indicated that slip-resistant shoes can reduce the risk of occupational slips and falls. Few studies, however, have examined the determinants of slip-resistant shoe use. This study examined the individual and workplace factors associated with slip-resistant shoe use. 475 wo...

This nested case-crossover study examined the association between rushing, distraction and walking on a contaminated floor and the rate of slipping, and whether the effects varied according to weekly hours worked, job tenure and use of slip-resistant shoes. At baseline, workers from 30 limited-service restaurants in the USA reported average work ho...

Slips and falls are a leading cause of injury at work. Few studies, however, have systematically examined risk factors of slipping outside the laboratory environment. This study examined the association between floor surface characteristics, slip-resistant shoes, floor cleaning frequency and the risk of slipping in limited-service restaurant worker...

The leading cause of injuries among restaurant workers is same-level falls, a significant proportion of which result from slipping. This study examines the experience of limited-service restaurant workers with slipping, their use of slip-resistant shoes, and their floor-cleaning practices. A total of 475 workers from 36 limited-service restaurants...

Slips, trips and falls (STF) are responsible for a substantial injury burden in the global workplace. Restaurant environments are challenged by STF. This study assessed individual and work environment factors related to slipping in US limited-service restaurant workers. Workers in 10 limited-service restaurants in Massachusetts were recruited to pa...

A portable inclineable articulated strut slip tester (PIAST) is a slipmeter that is widely used in the USA to measure coefficient of friction (COF) at the shoe sole and floor interface. A determination of a slip at the measurement interface, which is currently judged subjectively by operators, plays a crucial role in deciding the outcomes of a PIAS...

The aim of the study was to compare the performances of the Brungraber Mark II (BM II) and Mark III (BM III) slipmeters. Friction measurements with the two slipmeters were conducted in a laboratory using four footwear materials, four floor types, and three surface conditions. Both the coefficient of friction (COF) values obtained with the slipmeter...

Introduction Slips and falls are the leading cause of injury among restaurant workers in the U.S. This study examined the association between floor surface characteristics, shoe type, floor cleaning and the risk of slipping in limited-service restaurant workers. Method 362 workers from 32 limited-service restaurants in five states were recrui...

The significance of slipping and falling has been reported in the literature. It has also been shown that most slipping and falling incidences occur on level surfaces where floor slipperiness is a critical issue. Friction measurement is one of the major approaches in determining floor slipperiness. The Brungraber Mark II slipmeter is one of the fri...

For slips and falls, friction is widely used as an indicator of surface slipperiness. Surface parameters, including surface roughness and waviness, were shown to influence friction by correlating individual surface parameters with the measured friction. A collective input from multiple surface parameters as a predictor of friction, however, could p...

This study examined the association between circumstances of occupational same-level falls and the risk of wrist, ankle and hip fracture in women over 45 years of age. Cases of fractures and matched controls who suffered non-fracture injuries, all from same-level falls, were selected from workers' compensation claims data. Cases and controls were m...

If walkers can anticipate surface conditions, they can adjust their gait to help reduce the risk of a slip. This study investigated visual cues to slipperiness. Thirty-one participants made visually based judgements about 37 different floor surfaces. These judgements included ratings of slipperiness, reflectiveness, texture, traction, light/dark, l...

A portable inclinable articulated strut slip tester (PIAST) measures friction at the shoe and floor interface. The squeeze-film effect with the PIAST is excessive in representing a human strike. The goal of this study was to investigate the effect of the contact area size on friction for reducing the squeeze-film effect. The footwear pad area of th...

Friction variation has been related to employees' perception of slipperiness in a field study conducted in fast-food restaurants. However, details of friction variation in actual workplaces have not been reported in the literature. This field study investigated friction variations in 10 fast-food restaurants in the USA. The results indicated that f...

Workers pulling pallet trucks are likely to slip when pulling and stepping on a low-friction floor. This study investigated the slipping of male participants when pulling a pallet truck, walking backward, and stepping on either a dry, wet, or glycerol-contaminated vinyl surface. The weight of the load on the truck was either low (0 kg), medium (295...

The required friction coefficient is defined as the minimum friction needed at the shoe and floor interface to support human locomotion. The available friction is the maximum friction coefficient that can be supported without a slip at the shoe and floor interface. A statistical model was recently introduced to estimate the probability of slip and...

In 2007, the Bureau of Labor Statistics reported that the incidence rate of lost workday injuries from slips, trips and falls (STFs) on the same level in hospitals was 35.2 per 10,000 full-time equivalents (FTE), which was 75% greater than the average rate for all other private industries combined (20.2 per 10,000 FTEs). The objectives of this 10-y...

Although friction variation is speculated to be a significant contributor to slip and fall incidents, it has not been related to a measurement of slipperiness in the literature. This field study investigated the relationship among multiple friction variations, friction levels and the perception ratings of slipperiness in six major working areas of...

In preventing incidents of slips and falls, friction is widely used as an indicator of surface slipperiness. Surface feature parameters, including surface roughness and waviness, were shown to influence friction by correlating individual surface parameters with the measured friction. However, investigations of the collective input from multiple sur...

Objectives: This case control study examined the association between circumstances of falls and the risk of hip fracture in women over 45 years of age who suffered a same-level fall at work. Method: 373 cases of hip fracture and 1360 matched controls who suffered injuries other than fracture from same-level falls were selected from a large workers...

Slipping and falling are common incidents not only in workplaces but also on school campuses. In this research, we measured the coefficient of fiction of three floors commonly used on a college campus in Taiwan, under dry, wet, and sand-covered conditions using the Brungraber Mark II slipmeter. Leather, rubber, and polyvinyl chloride footwear sampl...

Floor slipperiness is a critical issue in slip and fall incidents which are a major source of occupational injuries. The objectives of the current study were to investigate if the protocols used in a field study conducted in Taiwan could be used in similar environments in the USA and whether consistent results could be obtained. Protocols used in t...

Falls are responsible for a substantial injury burden in the global workplace. Restaurant environments are particularly challenged by slips, trips, and falls. This study explored those factors that could influence workers' self-reports of slipperiness in U.S. fast-food restaurants. One hundred and twenty-six workers employed in 10 fast-food restaur...

The measured friction coefficients using almost all the commercially available slipmeters on ramps were different from those of the same tile on a horizontal surface because of the gravity. Establishing the mathematical relationship between the measurements on a ramp and on a level surface was essential in assessing the friction at the shoe–floor i...

It is a common belief that a person is more likely to slip when walking on an inclined surface than when walking on a level surface. Reports of friction measurements were common on horizontal surfaces but were rare on inclined surfaces. A slip measurement device reports different readings on the same surface with different inclined angles if the ef...

Several factors that might influence the outcomes of the slip index measurements with the Horizontal Pull Slipmeter were examined. These factors were either those not clearly specified in the operating guidelines of the device or those clearly specified but with a high variability in operator compliance. The results indicated that the shoe pad thic...

Urban taxi drivers differ from other professional drivers in their exposures to physical and psychosocial hazards in the work environment. Epidemiological data on low back pain (LBP) of this occupational group are very scarce. To examine LBP in taxi drivers and its association with prolonged driving and other occupational factors. We analyzed the c...

Epidemiologic evidence supporting optimal seating is limited and inconsistent. This cross-sectional study was conducted to examine the association between seat inclination, use of lumbar support, and the prevalence of clinically significant low-back pain among taxi drivers A digital inclinometer was used to measure inclinations of seat surfaces (th...

Many ladder accidents occur despite standards and regulations. The causes of these incidences may often be related to the setup and usage of the ladders. Slippage at the ladder base is one of the most common sources of accidents involving straight ladders. In a previous paper, we reported the coefficient of friction requirements at the bottom of th...

Straight ladder accidents are a major safety problem. As a leading cause of injuries involving straight ladders, slips at the ladder base occur when the required friction exceeds the available friction at the ladder shoe and floor interface. The objectives of this experiment were to measure the available friction at the base of a portable straight...

A statistical model to estimate the probability of slip and fall incidents is presented. In estimating such an event, the available friction is usually compared with the required friction for the activities. In the models available in the literature, only mean values were compared or a minimum threshold was used to represent the required friction....

Slips at the ladder bottom, which happen when the required friction to support activities on the ladder exceeds the available friction at the interface, are a major cause of injuries. The purpose of this study was to evaluate the effects of ladder inclined angle, climbing speed, ladder type, type of contact at the top of the ladder and body weight...

Surface roughness affects friction, but it is not clear which surface roughness characteristics are better correlated with friction. The surface roughness parameters generated from quarry tiles were correlated with the transition friction between the tiles and a commonly used sole testing material, Neolite, with three different mixtures of glycerol...

Slips and falls are major problems in occupational injuries in which floor slipperiness is a critical issue. Most of the studies on slipperiness assessments were conducted in laboratories. Field assessments are rarely reported in the literature. This study investigated floor slipperiness in seven kitchen areas of 10 western-style fast-food restaura...

Measurement of the coefficient of friction (COF) between the shoe/sole and the floor is essential in understanding the risk of slipping accidents. In this research, the COF of five floor materials commonly used on a university campus, under five surface conditions including dry and four liquid spillage conditions, were measured. The COF measurement...

Slips and falls are major problems in occupational injuries in which floor slipperiness is a critical issue. Most of the studies on slipperiness assessments were conducted in laboratories. Field assessments are rarely reported in the literature. This study investigated floor slipperiness in seven kitchen areas of 10 western-style fast-food restaura...

Friction is widely used as an indicator of surface slipperiness in preventing accidents in slips and falls. Surface texture affects friction, but it is not clear which surface characteristics are better correlated with friction. Highly correlated surface characteristics could be used as potential interventions to prevent slip and fall accidents. Th...

It is often difficult and expensive to make direct measurements of an individual's occupational or environmental exposures in large epidemiologic studies. In this study, we used information collected in validation studies to develop a prediction rule for assessing exposure in a study with no direct measurement. We established a prediction rule thro...

Background: It is often difficult and expensive to make direct measurements of an individual's occupational or environmental exposures in large epidemiologic studies. Methods: In this study, we used information collected in validation studies to develop a prediction rule for assessing exposure in a study with no direct measurement. We established a...

Surface roughness affects friction, so selection of floor surfaces with certain roughness characteristics could potentially reduce slip and fall accidents. This article summarizes the preferred surface microscopic geometric features that could increase friction on surfaces covered with liquid contaminants. Three types of surface features, represent...

To identify a set of important WBV predictors that could be used to develop a statistical instrument for exposure assessment in a large epidemiologic study, a total of 432 WBV measures were taken from a sample of 247 male drivers in Taipei City, Taiwan. In accordance with the ISO 2631-1 (1997) methods, we measured the frequency-weighted vertical ac...

A variety of slipmeters have been used to assess the slipperiness of floor surfaces. International standards for the operation of slipmeters describe the protocol for a single measurement. These standards usually do not cover some of the critical elements in safety assessment such as methods for the selection of measurement locations and the necess...

Surface roughness affects friction, but it is not clear which surface roughness characteristics are better correlated with friction. The dynamic friction between porcelain tiles and a commonly used shoe sole material, vulcanized rubber, under six test conditions with four different mixtures of glycerol and water as contaminants at the interface was...

Different institutions reported different results for friction measurements of identical material combination and surface conditions using identical slipmeters. The objective of this study was to evaluate three factors, slip criterion, sample, and time, that could contribute to such differences with two commonly used slipmeters, the Brungraber Mark...

Friction is widely used as an indicator of surface slipperiness in preventing accidents in slips and falls. Surface roughness affects friction, but it is not clear which surface roughness characteristics are better correlated with friction and, therefore, are preferred as potential interventions. The transition friction between quarry tiles and Neo...

The slip resistance of 16 commonly used footwear materials was measured with the Brungraber Mark II and the English XL on 3 floor surfaces under surface conditions of dry, wet, oily and oily wet. Three samples were used for each material combination and surface condition. The results of a one way ANOVA analysis indicated that the differences among...

Occupational slips, trips, and falls (STF) present a tremendous burden on the working people of the world. The precise contribution of slipping to this burden is not completely understood and significant questions exist regarding the definition and measurement of slipperiness. In an attempt to advance slipperiness measurement, a workshop symposium...