Ergonomics

Ergonomics

Deadman Controls on Lawn Mowers and Snowblowers
Triodyne Safety Brief v. 5 #2 (July 1988)

Ralph L. Barnett and Dennis B. Brickman

Consumer Product Safety Commission injury data are examined, and associated failure modes and effects verify the predictions contained in the literature. All failure modes involved ergonomic considerations. Zero mechanical state and its relationship with the current approach to lawn mower and snowblower maintenance are discussed.

Ergonomic Studies of Grip Strength -- Literature Review
Triodyne Safety Brief v. 6 # 2 (July 1990)

Dennis B. Brickman

A thorough study of literature on human strength reveals the need for a single data source which could be easily accessible to many researchers. Published data on one subset of this topic, ergonomic grip strength, is summarized under sixteen factors. Available data has been charted and documented in a way that will facilitate future reference and use.

Design Methodology for Predicting Ergonomic Grip Strength
Triodyne Safety Brief v. 8 #4 (July 1993), p.12-15.

Dennis B. Brickman

A design methodology has been developed to assist bioengineering practitioners in evaluating ergonomic grip strength data. The methodology employs a set of modifying factors to estimate the hand grip strength of a population. The grip strength modification factor approach allows designers and researchers to predict grip strength of individuals and of collections of homogeneous distribution in various situations.

Basic Considerations of Human Factors in Evaluation Systems, Information, and Displays
Triodyne Safety Abstract v. 1 #4 (November 1995)

Gary M. Hutter

Summary of a paper addressing display and control design as it relates to human information processing.

Hand Trajectories Under Free Fall
Triodyne Safety Brief v. 12 #2 (January 1997)

Ralph L. Barnett and Suzanne A. Glowiak

Can the hands elevate during a free fall scenario? This question arises in the design of fall intervention devices, during accident reconstruction and in the study of safe climbing strategies. This paper calculates the maximum simple reaction time that will enable the hands to elevate during a "drop" event.

Hand Motion During Trip and Fall Scenarios
Triodyne Safety Abstract v. 2 #4 (July 1997)

Ralph L. Barnett and Suzanne A. Glowiak

The full text of this paper was published in the American Society of Mechanical Engineers' International Mechanical Engineering Congress and Exposition in November 1997 and is available from Triodyne Inc.

Falling: The Cook County Illinois Experience
Triodyne Safety Bulletin v. 7 #1 (June 1998)

Claudine P. Giebs Myers and Peter J. Poczynok

An analysis of fall behavior as reported in the Cook County Verdict Reporter from 1991 and 1997.

Ladder Rung vs Siderail Hand Grip Strategies
Triodyne Safety Brief v. 16 #4 (April 2000)

Ralph L. Barnett and Peter J. Poczynok

When climbers lose their foothold on fixed, straight or extension ladders, the incipient fall may be arrested by gripping either the ladder rungs or siderails. Grasping the rungs provides an interference or power grip; squeezing the siderails provides a friction grip which is the primary focus of this paper. The falling scenario begins with free fall that lasts for the duration of the simple reaction time. Free fall is then decelerated by contravening friction forces derived from hand grip forces rapidly applied to the siderails. Using hand grip/time histories for various individuals, their fall distances were calculated for bare and gloved hands on a vertical steel fixed ladder. Sometimes the candidates could not arrest their falls; often their fall distance was too great to prevent ground impact. Under some circumstances, the vertical motion was brought under timely control. Although a rich literature is available for characterizing grip strength, data reflecting

How To Climb An Unsafe Ladder
Triodyne Safety Bulletin v. 9 #4 (January 2001)

Ralph L. Barnett

Weaknesses in a ladder structure are not always self revealing. Furthermore, a momentary loss of foot or hand control or even a patch of ice or grease may compromise a climber's safety. The proposed climbing strategy optimizes the safety profile. On the other hand, climbers must continue to follow the "classical ladder rules" dealing with ladder angle, overreaching, etc.

Evaluating Driver Response to a Life-Threatening Emergency: Issues of Behavior, Chance and Hindsight
Triodyne Safety Brief v. 18 #3 (April 2001)

Michael A. Dilich and Dror Kopernik, P.E.

Imagine driving a truck on a major highway at 45 mph when you spot a car on your right stopped in a driveway and poised to cross the road. It doesn’t move until suddenly, when you are only seconds away, it accelerates into your lane. You react aggressively by swerving to the left to get around it to avoid a collision. But it doesn’t stop! It keeps accelerating and you strike it broadside in the median to the left, killing the driver and seriously injuring a passenger. After the investigators have studied the accident in detail, you are criticized for using bad judgment and over-reacting. It can be shown that if you had done nothing more than continue to go straight, the car would have just cleared your lane before you arrived.

Forces and Injuries to the Human Body
Triodyne Safety Brief v. 20 #2 (April 2002)

Cheryl A. Pattin, Ph.D., P.E.

Biomechanics involves the application of mechanical engineering principles to describe forces associated with human movement and injury. The human body contains a number of tissues and organs, which respond in very specific ways to mechanical loading. Consequently, injury patterns observed following a trauma can provide important clues regarding the nature of the forces causing injury. Various aspects of applied forces and their relationship to injury patterns will be discussed including direction, severity, duration, and energetics.

Evaluating Driver Response to a Sudden Emergency: Issues of Expectancy, Emotional Arousal and Uncertainty
Triodyne Safety Brief v. 20 #4 (June 2002)

Michael A. Dilich, Dror Kopernik, P.E. and John M. Goebelbecker, P.E.

In April 2001, Triodyne published a Safety Brief entitled "Evaluating Driver Response to a Life-Threatening Emergency: Issues of Behavior, Chance and Hindsight," by Michael A. Dilich and Dror Kopernik. We have had so many requests for more information that we decided to reprint this longer article which Michael and Dror, along with John M. Goebelbecker, wrote for the Society of Automotive Engineers. This paper is reprinted, with permission, from SAE paper 2002-01-0089 ©2002 Society of Automotive Engineers, Inc. This paper was also presented to the Human Factors in Driving and Automotive Telematics Session on March 4, 2002 at the SAE World Congress in Detroit, MI.

"Slip and Fall" Theory - Extreme Order Statistics
Triodyne Safety Brief v. 21 #3 (September 2002)

Ralph Lipsey Barnett

Originally published in the International Journal of Occupational Safety and Ergonomics (JOSE) Volume 8, Number 2, 2002, this paper was the winner of the JOSE Best Paper Award for the years 2000 through 2002. Classical "slip and fall" analysis was reformulated in this paper to account for the stochastic nature of friction. As it turned out, the new theory, arising from this analysis, was a precise statement of the distribution function for the smallest value among n independent observations. This made it possible to invoke an important result from the asymptomatic theory of extreme order statistics that reduced the theory to a simple and elegant relationship among the probability of slipping, the critical friction criterion, the distance traveled by the walker, and the average, spread and asymmetry of the distribution of friction coefficients. This new theory reveals that short walks lead to fewer falls; low friction floors are sometimes better than high friction ones.

Human Push Capability
Triodyne Safety Brief v. 22 #1 (November 2002)

Ralph L. Barnett and Theodore Liber

Use of unassisted human push capability arises from time to time in the areas of crowd and animal control, the security of locked doors, the integrity of railings, the removal of tree stumps and entrenched vehicles, the maneuvering of furniture, and athletic pursuits such as football or wrestling. Depending on the scenario, human push capability involves strength, weight, weight distribution, push angle, footwear/floor friction, and the friction between the upper body and the pushed object. Simple models are used to establish the relationships among these factors.

Child Resistant Packaging - Regulations and Effectiveness, 1980-2002
Triodyne Safety Brief v. 23 #3 (May 2003)

Cheryl A. Pattin, Ph.D., P.E.

The Poison Prevention Packaging Act (PPPA) is a federally preemptive piece of legislation covering an ever expanding group of substances. The test methods used to establish compliance with the PPPA do not address the range of substances covered (e.g. liquids); the changing patterns of use of household substances such as increased use of liquid medications for children; or repeated access to and multiple reclosures of containers common in the home situation. To examine the effectiveness of the PPPA in addressing actual poisonings in children under 5, national databases from 1980 through March of 2002 were examined. The average age of children treated in hospitals was under 2, and fatalities due to Assisted access and Transfer of contents incidents were reported in children averaging under one year of age. These age ranges are below those of children used in child resistant packaging testing (3.5 to 4.25 years). More importantly, the average body weights -- directly related to the susceptibility to poisoning injury -- of children seen in hospitals is below the toxicity threshold set in the PPPA standard which is based on a 25 pound child. Training for children, the elderly, and parents would help increase awareness of Transfer of contents and assisted access poisonings, which are disproportionately represented in fatal poisoning incidents of young children.

Floor Reliability With Respect to "Slip and Fall"
Triodyne Safety Brief v. 24 #3 (November 2003)

Ralph Lipsey Barnett and Peter Joseph Poczynok

For a given community of walkers and a specific type of ambulation, force-plate studies have established the required level of horizontal resistance for stable locomotion. This stochastic floor loading is resisted by friction forces which must be great enough to prevent slipping. A statistical characterization of frictional resistance has recently been developed using extreme value statistics. Reliability theory provides a method for combining the floor loading and friction resistance which, for the first time, enables one to determine in a rational manner the probability of slipping. This paper presents a formula describing the "slip and fall" reliability of a floor/footwear couple.

Infant Pull Strength - Ability to Dislodge Crib Sheets
Triodyne Safety Brief v. 26 #1 (May 2004)

Ralph L. Barnett and Dennis B. Brickman

The suffocation of infants caused by crib sheet entanglement appears to be a nonproblem which has nevertheless resulted in a brouhaha that has incited remediation activities by the Good Housekeeping Institute (GHI), American Society for Testing Materials (ASTM), Consumer Product Safety Commission (CPSC), Juvenile Products Manufacturers Association (JPMA), crib sheet manufacturers, and product liability support professionals of different stripes. To show that the removal of crib sheets by infants is not a safety issue, one may establish that the problem is not reasonably foreseeable. Three approaches for doing this are described in this paper: anecdotal, simulation, and reliability. The reliability of a crib sheet is the probability that it will remain in situ when exposed to the community of infants. Application of the classical "load minus strength" analysis required new information on the pull strength of infants.