Mistakeproofing the design of construction processes.pdf

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Mistakeproofing The Design of
Construction Processes Using
Inventive Problem Solving (TRIZ)
Iris D. Tommelein
Sevilay Demirkesen
University of California, Berkeley
February 2018

©2018, CPWR-The Center for Construction Research and Training. All rights
reserved. CPWR is the research and training arm of NABTU. Production of this
document was supported by cooperative agreement OH 009762 from the
National Institute for Occupational Safety and Health (NIOSH). The contents are
solely the responsibility of the authors and do not necessarily represent the
official views of NIOSH.

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MISTAKEPROOFING THE DESIGN OF
CONSTRUCTION PROCESSES USING
INVENTIVE PROBLEM SOLVING (TRIZ)
Iris D. Tommelein and Sevilay Demirkesen
February 2018
CPWR Small Study Final Report
8484 Georgia Avenue, Suite 1000
www. cpwr.com • www.elcosh.org
TEL: 301.578.8500
© 2018, CPWR – The Center for Construction Research and Training. CPWR, the research and
training arm of the Building and Construction Trades Department, AFL-CIO, is uniquely situated
to serve construction workers, contractors, practitioners, and the scientific community. This
report was prepared by the authors noted. Funding for this research study was made possible by a
cooperative agreement (U60 OH009762, CFDA #93.262) with the National Institute for
Occupational Safety and Health (NIOSH). The contents are solely the responsibility of the
authors and do not necessarily represent the official views of NIOSH or CPWR.

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ABOUT THE PROJECT PRODUCTION SYSTEMS LABORATORY (P2SL) AT UC BERKELEY
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Laboratory: owners, regulators, architects, engineers, contractors, unions, suppliers, insurers, financiers,
etc.

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MISTAKEPROOFING THE DESIGN OF
CONSTRUCTION PROCESSES USING
INVENTIVE PROBLEM SOLVING (TRIZ)
Final Report for CPWR Small Study No. 16-3-PS
By:
Iris D. Tommelein and Sevilay Demirkesen
Department of Civil and Environmental Engineering
760 Davis Hall MC 1710
Berkeley, CA 94720-1710
For:
The Center for Construction Research and Training
8484 Georgia Avenue, Suite 1000
February 2018

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EXECUTIVE SUMMARY
This study set out to investigate and document how the principles and practices of so-called
mistakeproofing may be applied to improve safety and health performance—aspects of product-
and process quality—specifically in the construction industry.
Mistakeproofing (translated from the Japanese word poka yoke, a concept integral to the Toyota
Production System, defined as Lean) has been successfully used in numerous other industry
sectors. It can be used likewise in the construction industry.
A strength of Lean is its conceptual clarity on principles and the associated systems thinking it
promotes. In addition, supporting the principles are numerous tools and methods (such as
mistakeproofing), to be applied judiciously in any given system’s context and, when used in
combination, leveraging one-another.
The research defined the Lean principles of mistakeproofing, and also the principles of TRIZ
(Theory of Inventive Problem Solving) used for concept generation. Thirty examples, collected
by reading the literature and interviewing industry practitioners, were catalogued based on the
mistakeproofing and TRIZ principles they illustrate.
The need to mistakeproof everyday products and processes (tasks and work methods) may seem
obvious (or hopefully will appear obvious in hindsight), but mistakeproofing is by no means a
common practice. By defining the principles and offering examples, this report aims to
encourage broader awareness and use of it. Knowledgeable and purposeful use of
mistakeproofing principles and their practical application will lead to improved industry
performance in construction, as it has in other industries.

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TABLE OF CONTENTS
Executive Summary....................................................................................................................... iv
Table of Contents............................................................................................................................ v
List of Figures................................................................................................................................ vi
1. Introduction............................................................................................................................. 7
1.1. Background on Lean Thinking in Construction............................................................... 7
1.2. Background on Mistakeproofing...................................................................................... 8
1.3. Overview of Report........................................................................................................ 10
2. Research Objectives, Goal, and Approach............................................................................ 11
3. Mistakeproofing.................................................................................................................... 11
3.1. Definition of Mistakeproofing ....................................................................................... 11
3.2. Principles of Mistakeproofing........................................................................................ 13
3.3. Concepts Related to Mistakeproofing............................................................................ 17
3.3.1. Mistakes vs Process Capability............................................................................... 17
3.3.2. 5 WHYs, Failure Modes and Effects Analysis (FMEA), and Small Wins............. 19
3.3.3. Hierarchy of Hazard Controls................................................................................. 21
4. Theory of Inventive Problem Solving (TRIZ)...................................................................... 22
4.1. Definition of TRIZ ......................................................................................................... 22
4.2. 40 Principles of TRIZ..................................................................................................... 22
5. Example Applications of Principles of Mistakeproofing and TRIZ..................................... 24
6. Research Findings and Conclusions ..................................................................................... 25
7. Acknowledgments................................................................................................................. 26
APPENDIX I: Glossary................................................................................................................ 27
APPENDIX II: References and Selected Bibliography................................................................ 32
APPENDIX III: 40 TRIZ Principles............................................................................................. 37
APPENDIX IV: Catalog with Mistakeproofing Examples .......................................................... 42

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LIST OF FIGURES
Figure 1: Color Code for Each of Six Mistakeproofing Principles .............................................. 13
Figure 2: Pneumatic Nail Gun in Use (en.wikipedia.org/wiki/Nail_gun) .................................... 14
Figure 3: Nail in Hand (Hellerhoff (2012) upload.wikimedia.org/
wikipedia/commons/f/f8/Nagel_von_Schussapparat_in_Hand_-_Roe_ap.jpg)........................... 14
Figure 4: Color-coded Screws (and Corresponding Bin Labels) are Easy to Match/Tell Apart
(facilitate recognition) (Source: Iris Tommelein)......................................................................... 15
Figure 5: Fall Protection System .................................................................................................. 15
Figure 6: Applicability of Mistakeproofing Principles to Work Operations (adapted from
Godfrey et al. 2005)...................................................................................................................... 16
Figure 7: “5 Why” Investigation Questions (Source: Scholtes, P.R. (1998). The Leader’s
Handbook. McGraw-Hill, Figure 20-1)........................................................................................ 20
Figure 8: Hierarchy of Hazard Controls (Source: www.osha.gov/shpguidelines/hazard-
prevention.html after Peterson 1973)............................................................................................ 21
Figure 9: Prism of TRIZ Problem Solving Solutions (Oxford Creativity,
(upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Prism_of_TRIZ_Oxford_Creativity.png/
640px-Prism_of_TRIZ_Oxford_Creativity.png).......................................................................... 23

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1. INTRODUCTION
1.1. Background on Lean Thinking in Construction
This study set out to investigate and document how the principles and practices of so-called
mistakeproofing may be applied to improve safety and health performance—aspects of product-
and process quality—specifically in the construction industry. The thought process of
mistakeproofing is in numerous ways aligned with the safety-mindedness that OSHA is
promoting to achieve higher standards of performance in the construction industry, i.e., lowering
fatality-, illness-, and injury rates. However, their origins and focus of practice appear to differ.
For example, mistakeproofing is concerned with preventing mistakes of any kind, while safety-
mindedness tends to focus on hazardous situations and incidents. This notwithstanding,
mistakeproofing and OSHA’s pursuits are aligned in that OSHA (2016) states “The
recommended practices emphasize a proactive approach to managing occupational safety and
health. Traditional approaches are often reactive—that is, actions are taken only after a worker is
injured or becomes sick, a new standard or regulation is published, or an outside inspection finds
a problem that must be fixed. Finding and fixing hazards before they cause injury or illness is a
far more effective approach. Doing so avoids the direct and indirect costs of worker injuries and
illnesses, and promotes a positive work environment.”
Mistakeproofing (or fail-safing) is the English translation of the Japanese term poka yoke. Poka
yoke has been used for many years at Toyota and is integral to the Toyota Production System
(TPS). Toyota’s Production System was singled out and gained notoriety in the 1980s for its
superior performance compared to other companies (American as well as Japanese). John
Krafcik, who served on the MIT-Harvard team in the 1980s that studied Japanese practices in
automobile manufacturing (Womack et al. 1989), therefore coined the term “Lean Production” to
refer to its systemic approach, while also differentiating it from mass- and from craft production.
With “Lean” he highlighted that Toyota uses less of everything by comparison with US
producers: fewer materials, fewer human resources, fewer machines, less money, less time, and
less space, to engineer and manufacture products of high quality for their customers. The Lean
Enterprise Institute (LEI 2016) thus defines the term Lean as “Creating more value for customers
with fewer resources.” Lean Thinking is fundamentally rooted in (1) respect for people and
(2) continuous improvement.
Numerous books that have since been written to describe the TPS principles and methods (e.g.,
Ohno 1988, Liker 2004, Liker and Meier 2005). A strength of the TPS is its conceptual clarity on
principles and the associated holistic “systems thinking” it promotes. In addition, supporting the

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principles are numerous tools and methods (such as mistakeproofing), to be applied judiciously
in any given system’s context and, when used in combination, leveraging one-another.
Many researchers and practitioners have applied Lean Thinking very successfully in a variety of
domains other than automobile manufacturing (e.g., service sectors including healthcare). The
application of Lean Thinking to construction, so-called Lean Construction, has been pursued by
researchers and practitioners since the early 1990s (e.g., Koskela 1992, Ballard et al. 2002,
Koskela et al. 2002). They formed a community of practice called the International Group for
Lean Construction (IGLC) that has been active since 1993 (www.iglc.net).
Gambatese and Pestan (2014) described how Lean Design and Construction relates to
construction worker safety. Their report mentions once (on p. 12) the practice of mistakeproofing
but offered no further detail on this Lean method. Research by others has shown correlation
between the adoption of Lean Thinking, for example using the Last Planner® System (Ballard
2000), and improved safety performance on construction sites, and an agenda on Lean safety is
being pursued (e.g., Howell et al. 2002). Mistakeproofing fits into that agenda.
All too many aspects of the construction industry today are still based on craft production, and
inefficiencies and incidents abound. On a day-to-day basis, workers face the numerous
challenges and characteristics of one-off production but lack individual training and team-wide
systemic thinking to help improve performance overall.
Recognizing the means Lean Thinking offers, this report will introduce mistakeproofing
principles and examples in the architecture-engineering-construction (AEC) industry. In doing
so, it aims to drive industry innovation in developing products and processes of greater quality
and thereby contribute to construction industry performance improvement.
1.2. Background on Mistakeproofing
While the concept of mistakeproofing has been around at least since the 1980s, mentioned in the
early work by Suzaki (1985) and Shingo (1986) who wrote the book Zero Quality Control, it
does not appear to be commonly understood and applied in the construction industry. Where it
has been used in other industry sectors (manufacturing, healthcare, and many more) it has
yielded significant benefits. Reasonably one may therefore expect that the construction industry
will benefit from its use as well.
Many online glossaries with lean production terms include mistakeproofing or poka yoke, and at
least one web site has been dedicated to this topic (www.mistakeproofing.com). However, while
the use of mistakeproofing has been mentioned in the construction literature (e.g., dos Santos and

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Powell 1999, Tommelein 2008a, 2008b), it does not appear to be have been systematically
researched nor is it practiced as widely as it can be. Owners, designers, contractors, engineers,
and others involved in the architecture-engineering-construction (AEC) industry need to know
what and where opportunities exist for mistakeproofing, to gauge what value may stem from it,
and to sharpen everyone’s thinking about opportunities to mistakeproof AEC products and
processes. Mistakeproofing is relevant and applies to tasks, operations, and projects small and
large, simple and complex, and all sectors of the construction industry (e.g., Wood 1986,
McDonald 1998).
Mistakeproofing is particularly well suited for the AEC industry with its low-volume and mixed
production systems, where other improvement methods such as Statistical Process Control (SPC)
and Six Sigma have not gained much traction. Construction practitioners who tried using SPC
found they could not implement it widely due to lack of a statistically significant amount of data
and un-timeliness of findings that result from after-the-fact data processing. The applicability of
Lean methods to events that occur only once or occasionally is relevant especially in
construction project settings. Construction activities get performed once, or possibly repeated a
few times, but then finish and get followed by a follow-on activities well before statistics can be
used.
Mistakeproofing can be thought of as a practice akin to constructability, that is, changing a
design so that it can be built “better”—more safely, easily, cost effectively, so it will last longer,
etc. However, it differs from constructability in two regards. First, the goal of mistakeproofing is
to improve system performance by eliminating waste—avoiding product and process defects
(e.g., creation of hazardous situations), reducing variation, and not tolerating poor quality.
Second, efforts at mistakeproofing do not necessarily coincide with the timing of constructability
review in a project’s delivery process. Simply put, pursuing constructability sometimes means
cutting costs after a design already has been substantially developed but exceeds budget. In
contrast, mistakeproofing is a practice for all project participants—designers, manufacturers,
fabricators, builders, owner-operators, and others—to pursue in their day-to-day work and
throughout project delivery. Mistakeproofing is a method for Prevention through Design (PtD), a
practice that has been advanced in recent years in the AEC industry, but has yet a long way to go
before it will be part of everyday thinking in practice (Duffy 2004, Shulte et al. 2008, NIOSH
2014).
In many regards, mistakeproofing complements SPC (e.g., Baudin 2001, Stewart and Grout
2001). It is a method for so-called error management (Tommelein 2017). Indeed, the systems
view that Lean thinkers adopts, recognizes that each individual person works in a larger,
complex whole where—despite best efforts—errors will never be 100% preventable.

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Mistakeproofing requires a different way of thinking about production processes and its
constituent operations, and it can be applied fittingly in construction (for a sneak preview, see the
example in Appendix IV). It offers an alternative to the all-too-prevalent “regulate, enforce, and
punish” approaches used in construction safety management.
Stewart and Grout (2001) also mention that mistakeproofing may not be taken seriously enough,
especially by academics, because of its lack of theoretical grounding and its apparent simplicity
of solutions. They state that this lack of grounding of mistakeproofing is due to its boundary-
spanning nature: it lies, not in “operations management, management science, operations
research, industrial engineering, and statistics” but in “qualitative subject of human
psychology…” and “…cognitive science.” The same can be said, at least to a degree, about
theoretical grounding for safety management. That literature includes work on human error and
cognitive systems engineering (e.g., Dekker2004, 2006, 2012, 2014, Rasmussen 1982,
Rasmussen et al. 1994, and Reason 1990) as well as on project production system design (e.g.,
Mitropoulos 2014, Memarian and Mitropoulos 2013, 2015).
Without a doubt, mistakeproofing has been and is being applied in the AEC industry. However,
it appears that barriers to its widespread implementation may exist. Barriers such a lack of
knowledge and understanding of its principles can be overcome by increasing industry awareness
by means of dissemination of reports such as this one. Once practitioners will have learned to
recognize mistakeproofing devices, their new mind-set will enable them to spot numerous
opportunities available to mistakeproof their workplace. Though some mistakeproofing practices
do require investment in new product development, they will find that many can be implemented
at a minimal cost.
1.3. Overview of Report
Section 2 of this report summarizes the research objectives, goal, and approach. Section 3
defines mistakeproofing, expands on its 6 principles, and illustrates them with a few examples
(Appendix IV presents a richer set of 30 detailed examples that use these principles). Section
3 also ties-in several related concepts. Subsequently, the report ventures into describing a
rational way of coming up with (new) mistakeproofing practices. To this end, Section 4 defines
the concept generation method called TRIZ (the Theory of Inventive Problem Solving) and
expands on its 40 principles. Section 5 and examples in Appendix IV illustrate the application of
TRIZ to create new means for mistakeproofing. Section 6 offers key findings with
recommendations on the further use of mistakeproofing in the construction industry, and
concludes the report.

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Appendix I provides a glossary of terms related to mistakeproofing. Appendix II lists the
references cited in this report as well as a selected bibliography. Appendix III enumerates the 40
TRIZ principles. Last but not least, Appendix IV includes 30 examples of mistakeproofing
practices categorized first by mistakeproofing principle exemplified, and then by the TRIZ
principles exemplified.
2. RESEARCH OBJECTIVES, GOAL, AND APPROACH
The objectives of this research study were to shine the limelight on the concept of
mistakeproofing and its application specifically to improve safety performance in the
construction industry, to explain its underlying principles, and to provide examples to illustrate
how it is used in practice.
The goal of the research is to inspire workers so that they will think routinely of new ways to use
the method in order to mistakeproof their everyday environment.
The researchers conducted descriptive research of theory and practice. They approached this
study by reviewing the academic and professional literature, as well as numerous online
postings, for references on the principles and examples of mistakeproofing. They contacted
industry professionals in construction and manufacturing companies, spoke with them over the
phone, and visited their facilities to learn about mistakeproofing practices and to identify specific
examples. The researchers assembled a set of mistakeproofing examples and then classified these
examples based on the mistakeproofing principle(s) applied. They also classified them based on
the TRIZ principles applied. Finally, the researchers detailed a rich selection of examples
(provided in Appendix IV) and wrote this report.
3. MISTAKEPROOFING
3.1. Definition of Mistakeproofing
Mistakeproofing (also called errorproofing, as the terms mistake and error are used
interchangeably) “is the use of any automatic device or method that either makes it impossible
for an error to occur or makes the error immediately obvious once it has occurred (ASQ.org).”
The objective of mistakeproofing is to prevent errors from turning into defect, in order to reduce
(at best: eliminate altogether) quality defects in construction products and processes.
Unquestionably, safety is a metric of quality, so mistakes and defects include those that are
safety-related and might lead to hazards, incidents, or chronic pain.
In the strict sense of this definition, mistakeproofing is about managing mistakes being made by
people, recognizing that to err is human. It is a Lean method for error management as noted in

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Tommelein (2017). However, when working back from the objective stated, to reduce defects,
one recognizes that defects may also be caused by machines or processes that cannot consistently
produce quality output. While considering performance improvement opportunities in the
construction industry, it may make sense to broaden the notion of mistakeproofing, by including
concern for ascertaining so-called process capability (more on this in Section 3.3.1).
Mistakeproofing is rooted in the concept zero quality control developed in Shingo’s (1986) so-
named book Zero Quality Control: Source Inspection and the Poka-yoke System. The back cover
reads, “Defects = 0 is absolutely possible!” Shingo critiqued the use of SPC and was set on
eliminating ad-hoc quality control (QC). Translated to the construction industry, such ad-hoc QC
includes the punch-list process and corresponding rework that everyone appears to take for
granted. He advised that source inspection and successive inspection be implemented in order to
ascertain that only quality products would be passed along the assembly line, recognizing that
errors would occur.
Shingo (op. cit., p. 82) stated, “I claim that it is impossible to eliminate all errors from any task
performed by humans. Indeed, inadvertent errors are both possible and inevitable. Indeed, the
systems view that Lean thinkers adopts, recognizes that each individual person works in a larger,
complex whole where—despite best efforts—errors will never be 100% preventable. Certainly
there is no reason why the same error should occur more than once; recurrence is especially bad.
“Yet errors will not turn into defects if feedback and action take place at the error stage. In this
way, I am advocating the elimination of defects by clearly distinguishing between errors and
defects, i.e., between causes and effects.” Shingo advocated the use of mistakeproofing to reduce
the possibility of errors occurring, to make errors—should they occur—easily detectable, and to
mitigate their effects so they would not turn into defects. As a result, mistakeproofing reduces
the need for inspection.
Defined by principles, mistakeproofing is a mindset; it requires Lean Thinking. Mistakeproofing
shuns the blame mentality. Instead it aims to develop a mind-set in individuals and teams and
equip them with principles to manage mistakes using prevention combined with increased
awareness to respond judiciously to unforeseen conditions when mistakes cannot a priori be
prevented but their detrimental impact can possibly be alleviated. In other words,
mistakeproofing is about seeing (or learning to see) where something may go awry, figuring out
the reasons why a defect may occur and how the causes may be prevented, and then taking action
to prevent these anticipated occurrences. The range of action that any one individual can take to
mistakeproof a product or process will vary depending on their responsibility and authority
within their organization. In Lean organizations, everyone is expected to be involved.

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3.2. Principles of Mistakeproofing
Mistakeproofing is based on 6 principles (e.g., Shingo 1986, Shimbun 1988, McMahon 2016). In
the remainder of this report and in Appendix IV where examples are detailed, the authors classify
them using the color coding shown in Figure 1.
Figure 1: Color Code for Each of Six Mistakeproofing Principles
Quite a few examples have different aspects to them, each of which can illustrate a different
principle. Of note is that the principles are not as crisply defined as they could be. People may
argue about an example exemplifying one principle or another. Practically speaking, the goal of
showing examples is not to get into such arguments but rather to help readers practice their
ability to see and recognize mistakeproofing practices in their everyday environment, and then
leverage that ability to create their own mistakeproofing applications.
The 6 mistakeproofing principles are:
1. Elimination (paraphrased as “don’t do it anymore”) is to remove the possibility of an error
occurring in a task of a process by redesigning the product or process so that the task (or
associated product part) is no longer necessary. For example:
• Several hazards stemming from the use of electrical extension cords to power tools
(e.g., tripping over them) are eliminated by replacing corded tools with battery-
powered ones (see Example 1 in Appendix IV).
• Several hazards to which ironworkers are exposed while welding structural steel, are
eliminated by redesigning the structural system to use, not welded connections, but
bolted connections instead (a new process and new parts).
2. Prevention (“make sure it can never be done wrong”) is to design and engineer the product
or process so that it is impossible to make a mistake at all. For example:
• A vehicle’s engine will not start unless the driver has a foot on the brakes (limit
switch).
• A three-pronged electrical plug can be inserted into a power outlet in only one way
(part asymmetry).

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3. Replacement (“use something better”) is to substitute one process with a more reliable
process to improve consistency. For example:
• Instead of using ladders on site, use scissor lifts.
• Instead of surveying using a theodolite, use an electronic total station instead
(automation).
• An existing planning system for on-site trade coordination may be replaced by the
Last Planner System (Ballard 2000) to promote work flow reliability and enhance
safety performance.
• Rather than use a tape measure to measure the spacing between parts repeatedly, one
part at a time, use a jig to space parts evenly.
4. Facilitation (“catch people’s attention, help them make fewer mistakes”) is to use various
means (e.g., sensory input) to make tasks easier to perform. For example:
• Construction equipment has a backup signal (auditory input) to alert people nearby
that it is moving and the driver’s view going backward is restricted.
• The trigger on a nail gun works only when the nail gun is contact with a surface so it
cannot be used to shoot in the air (Figure 2), though note that the surface can be skin
(Figure 3).
Figure 2: Pneumatic Nail Gun in Use
(en.wikipedia.org/wiki/Nail_gun)
Figure 3: Nail in Hand (Hellerhoff
(2012) upload.wikimedia.org/
wikipedia/commons/f/f8/Nagel_von_Sch
ussapparat_in_Hand_-_Roe_ap.jpg)

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• Create a visual workplace by using color coding: screws of different color are easy to
tell apart (Figure 4).
Figure 4: Color-coded Screws (and Corresponding Bin Labels) are Easy to Match/Tell Apart
(facilitate recognition) (Source: Iris Tommelein)
5. Detection (“notice what is going wrong and stop it”) is to identify a mistake promptly so that
a person can quickly correct it and thereby avoid that the error may turn into a defect (Shingo
1986). Examples are:
• Rumble strips on highways alert drivers when they are crossing lanes and may run off
the road (sensory feedback)
6. Mitigation (“don’t let the situation get too bad”) is to minimize the effects of errors. Grout
(2003) calls this “designing benign failures.” Examples are:
• Electrical fuses prevent overloading circuits resulting from shorts (McMahon 2016).
• Personal Protection Equipment (PPE) to various degrees protects a person by
reducing the effect of any impact (e.g., a hard hat cushions the blow on the head from
the impact of a falling object).
• Fall protection systems protect workers from falls and, related, to prevent damage
caused by falling objects (Figure 5). As recorded by the Bureau of Labor Statistics
(BLS 2016), fatalities caused by falls are the main cause of death for construction
workers. In 2014, 337 of the 874 construction fatalities stemmed from falls from
elevation. Hence, there is a great demand for such systems.
Figure 5: Fall Protection System
(butlermfg.com/en/products_systems/roof_systems/skyweb_ii_skyweb)

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Figure 6 lays out these 6 principles based on when they apply in the course of executing work
(work operations). Elimination, Prevention, Replacement, and Facilitation are means to avoid
the occurrence of mistakes. Detection and Mitigation are means to minimize the effects of
mistakes once they occur. In any one of these cases, mistakeproofing devices and processes
should be designed so that they meet three criteria: (1) be simple, (2) be infallible, (3) be used
effortlessly (e.g., McMurray and Garcia 2016).
Figure 6: Applicability of Mistakeproofing Principles to Work Operations (adapted from
Godfrey et al. 2005)
The 6 mistakeproofing principles were color-coded in order of decreasing preference for their
application. On one end of the range is Elimination (dark green in Figure 1 and 4), the most
desired of all as it makes not only the hazard associated with a task, but the entire task go away.
Mistakeproof processes are intolerant of defects. At best they are designed so that no mistakes
can be made; at least they reduce the chance of mistakes being made. On the other end of the
range is Mitigation (reddish in Figures 1 and 4), as it should be the last principle considered to
mistakeproof a product or process, when other ones cannot be made to work in the current
situation. NPD-solutions (n.d.) among others note, “[i]deally, mistakeproofing should be
considered during the development of a new product to maximize opportunities to mistake-proof
through design of the product and the process (elimination, prevention, replacement, and
facilitation). Once the product is designed and the process is selected, mistakeproofing
opportunities are more limited ([…] detection and mitigation).”

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Among the numerous examples of mistakeproofing documented in the course of this research
project, and singling out safety-related devices and practices, the authors found that many are
Mitigation related (e.g., PPE). Mitigation (and Detection) are after-the-fact (reactive, before the
mistake occur has occurred) mistakeproofing approaches and therefore not the best. The before-
the-fact (proactive, before the mistake occurs) mistakeproofing approaches have been gaining
prominence in the construction safety community through efforts such as Prevention through
Design (PtD) (NIOSH 2014, Schulte et al. 2008), Our industry can do a lot more in this regard to
make its products and processes safer.
These 6 principles all focus on the worker in their environment. The aim is to mistakeproof the
tasks workers perform in the process of delivering a product or service. To be of quality, the
delivery process must also consider the recipient of that product/service, namely the customer.
Some mistakeproofing practitioners (e.g., in healthcare, Gregory and Kaprielian 2016) add
another principle, namely “Patient Involvement” as the patient is the customer of the healthcare
provider. That principle is addressed by Shingo’s concept of successive inspection and applies in
construction as well. To deliver a quality product to a customer, one must know what the
customer wants and allow the customer to express their concerns and have a say in making an
assessment of the quality of the product or service received.
3.3. Concepts Related to Mistakeproofing
A number of concepts from quality management and other schools of thought also pertain to
creating defect-free products and processes, as is the case for mistakeproofing.
3.3.1. Mistakes vs Process Capability
Although the term process capability is not commonly used in the construction industry, it helps
make a crucial distinction between it and the occurrence of mistakes, that is important in the
pursuit of continuous improvement. Process capability has been established (at a certain level of
performance) if anyone (at some level of skill, as per the process specifications) doing the job
will consistently meet the expected quality standard.
Process capability affects all workers (e.g., exposure to silica fumes from grinding or drilling
into stone or concrete) and must therefore be established with worker safety and health in mind.
The same is true for design of operations by means of which one can, for example, shift the kinds
of hazards workers are exposed to (installing duct work at ground level to fit under a raised floor
system is less hazard-prone that working overhead on duct installation, but it is hard on the
knees).

18
By definition, process capability describes the variation in a property of the output of a process
(e.g., the geometry of the material produced) that is achieved under normal operating conditions.
This definition pertaining to geometry equally applies to any material, resource, or process
property such as duration, temperature, impact strength, etc. (P2SL Glossary 2017).
The term “normal operating conditions” presumes that the workers involved are qualified to do
the work and make no mistakes. By definition, a mistake is an inadvertent human action that
may lead to a defect in a process or product, or harm to a person. This brings us back to
mistakeproofing, which is to design products or processes to eliminate (or at least to reduce) the
probability or impact of mistakes and defects in use or execution. When people are not
successful (mistakes occur or the outcome produced is defective) in executing a certain process
or constructing a certain product to the desired quality standard, a number of causes may be in
play:
1. The process they are to follow is not capable—irrespectively of the person involved—of
consistently achieving the desired outcome, in which case process capability must be
improved. For example:
• When using a panelized concrete formwork system there will be joints through which
concrete or grout can seep. Excessive formwork leakage may be considered a defect. As
long as the workers have erected the formwork “the correct way,” such leakage is not to
be attributed to human mistake. How much the forms will leak is matter of process
capability: it will vary by formwork system selected, methods used to put it in place, as
well as precautions taken to prevent leakage from occurring.
Such precautionary measures do not fall under the realm of mistakeproofing (in the strict
sense, because they do not pertain to human error), nevertheless, why not consider them
if mistakeproofing principles can address them?
Following the same argument, the authors see no reason to single out opportunities to
improve safety in performing a task from opportunities to improve quality in general, and
therefore use the term “integrated task planning” to denote that all aspects of a task,
separately, together with others, and holistically, are to be considered for improvement
(by mistakeproofing or other means).
2. The quality standard (for construction) may not have been articulated or made clear to them,
that is, they may not know what is expected and need to learn it.
3. Perhaps they knew but forgot (an opportunity for mistakeproofing).
4. Not all requirements for executing the selected, capable process are in place. E.g., some
inputs provided may be of inferior quality.

19
5. The process is capable, people know the process and its quality standard, and all
requirements are satisfied, and yet they may still make mistakes in the course of executing
the process (a clear need for mistakeproofing). For example:
• Building on the earlier example of formwork erection, if a worker leaves off a clamp to
hold panels together (and that causes leakage), that would be a mistake.
Both process capability and human error affect product and process quality. In construction
projects, it is often taken for granted that process capability is established, processes are in place,
and workers will consistently follow them. From the author’s experience and direct observation
of how work gets done on site and off site, however, it is clear that specific work methods and
quality expectations are not necessarily spelled out nor systematically followed; enforcement is
often lax. When worker preferences govern over how they go about their work, significant
differences may exist between what one worker accomplishes vs. another one. This makes it
difficult to establish a standard for performance relative to which improvements may be
assessed.
One way forward is to stepwise establish a quality processes to deliver quality products or
services to customers. Baudin (2001) suggests that the first step is to establish process capability.
In the case of repeatable processes, this may be done by setting expectations (e.g., setting upper
and lower bounds on acceptable performance and applying Six Sigma methods), identifying
recurring defects, and remediating them.
Once process capability has been established, however, people involved in the process may still
make occasional mistakes. Ideally, systems will be designed so that no mistakes can be made,
however, to err is human. Given that mistakes will occur, the subsequent steps are therefore to
make it quick and easy to detect them so that remedial action can be taken and mistakes will not
become defects. Here is where Lean methods such as one-piece flow, first-in first-out, cellular
manufacturing, 5 WHYs, and small wins come in. The latter two are explained next.
3.3.2. 5 WHYs, Failure Modes and Effects Analysis (FMEA), and Small Wins
When a situation is unsatisfactory to someone for some reason, people should express a concern.
A concern is precautionary in nature: the situation may not be deemed problematic (yet) and no
incident has as of yet occurred, but it is important to express it, because that is the start to
identify causes and potential countermeasures (e.g., use mistakeproofing), and implement them
before the problem arises or incident occurs.
A countermeasure is a corrective action taken in response to the identification of a deviation
from a desired expected condition (a standard condition) in an attempt to prevent that deviation

20
from reoccurring. Whether or not that attempt is successful in the short- or long term will have to
bear out. Recognizing that further improvements, even better than the current corrective action,
may exist and be identified at a later time, Lean practitioners therefore opt to use the term
countermeasure rather than say “a problem is solved.” It indicates their ongoing and never-
ending pursuit of continuous improvement.
The Lean method called 5 WHYs is one of several methods to identify root causes of product- or
process failures. Ohno (1988) defines this concept in greater detail. The essence is that one must
ask Why? successively—at least 5 times—in order to get beyond the symptoms of a problem that
can be addressed with a local countermeasure, to uncover one or several of the problem’s root
causes so that they may be addressed by using more systemic, longer-lasting countermeasures
(Figure 7).
Figure 7: “5 Why” Investigation Questions (Source: Scholtes, P.R. (1998). The Leader’s
Handbook. McGraw-Hill, Figure 20-1)
The Failure Modes and Effects Analysis (FMEA) method offers a systematic way to describe
failures and pursue remedial action. The FMEA analyst must identify all possible ways in which
a product or process can fail (so-called failure modes) and then assign a likelihood of occurrence
and severity to each one. Based on these, the analyst can compute a relative Risk Priority
Number (RPN) and use that, in combination with other considerations, to prioritize which failure
mode to address first.
From the perspective of a Lean thinker, note that any improvement opportunity (including
potential or occurring problems), big or small, is worth addressing. Lean thinkers at all levels in
their organization are encouraged to pursue not only high risk challenges (presumably with big
wins) but also small wins (Amabile and Kramer 2011). Any improvement is a win and many
small ones accumulate over time. More importantly, Lean organizations want everyone trained

21
and involved in pursuing improvement opportunities in a systematic way. Alertness to small
wins sharpens people’s skills at finding improvement opportunities in general (e.g., Akers 2011).
The next task is to explore each of the 6 mistakeproofing principles and identify means by which
they may be achieved. This requires a concept generation method such as TRIZ (expanded on in
Section 4). A means can then be selected and implemented as a countermeasure. Further
observation of the implementation may lead to yet new insights into how yet further means for
mistakeproofing may be deployed.
Before proceeding with TRIZ, however, the next section briefly describes how mistakeproofing
relates to OSHA’s well-known Hierarchy of Hazard Controls.
3.3.3. Hierarchy of Hazard Controls
The 6 mistakeproofing principles as described align to some degree with OSHA’s Hierarchy of
Hazard Controls. OSHA’s hierarchy includes five levels. Figure 8 depicts it by an upside-down
triangle to stress that the top level (elimination) is deemed most effective and the bottom one
(PPE) least effective.
Figure 8: Hierarchy of Hazard Controls (Source: www.osha.gov/shpguidelines/hazard-
prevention.html after Peterson 1973)
The 5 levels in the Hierarchy of Hazard Controls are:
1. Elimination is about preventatively, on paper and physically removing any hazard so it will
no longer be part of the design.
2. Substitution is about preventatively replacing a product or process with another one that is
deemed less hazardous or risky.

22
3. Engineering Controls is about isolating people from the hazard and guarding them.
4. Administrative Controls is about changing the way people work, by providing training and
scheduling work with safety in mind
5. Personal Protective Equipment (PPE) is about shielding the worker from hazards should
incidents occur.
Particularly the first two match their namesake principles of mistakeproofing, though OSHA is
of course safety and health focused. Both Elimination and Substitution are about “designing it
out.” The other three in the Hierarchy appear more narrowly focused than the principles of
mistakeproofing are.
4. THEORY OF INVENTIVE PROBLEM SOLVING (TRIZ)
Knowing the principles of mistakeproofing will help people recognize what practices have been
implemented. This in turn will help them do their own mistakeproofing by simply copying
examples from one application to another, or perhaps extrapolating. But when these do not work,
a method is needed to generate new concepts to mistakeproof an existing product or process, or
generate altogether new mistakeproofed-ones. The design methodology called the “Theory
Inventive Problem Solving” or TRIZ may serve as a means to this end (Cerit et al. 2014).
4.1. Definition of TRIZ
TRIZ is the Russian acronym that is translated in English as the Theory of Inventive Problem
Solving (TIPS). It was developed by Genrich Altshuller in 1946 and evolved over the course of
about 50 years (Altshuller 1997, 1999, Souchkov 2008 rev. 2015). Altshuller had been working
in a patent office and studied what defined an innovation. Over this period of time, Altshuller
and colleagues developed not only principles but also Algorithms for Inventive Problem Solving
(ARIZ) (e.g., Altshuller 1999, Marconi 1998) and related methods to foster innovative thinking.
The focus in this report in on using the 40 TRIZ Principles and use them to generate
mistakeproofing concepts. The notion of using TRIZ as a Lean Thinking tool is not new (e.g.,
Ikovenko 2005).
4.2. 40 Principles of TRIZ
The challenge stems from the fact that, when designing something new, designers face
requirements and constraints that may be contradictory. They must then must negotiate tradeoffs.
In the TRIZ context, these are called contradictions. To offer an example from Toyota, engineer
Suzuki who spearheaded the Lexus program, became known for his uncompromising stance on

23
seemingly conflicting design requirements (e.g., develop a car that can reach high top speeds, yet
have low fuel consumption) , Suzuki’s YETs (Liker 2004 p. 43-50).
Altshuller (1999 pp. 287-289) identified a set of 40 TRIZ Principles that can be used as a toolbox
to resolve contradictions and thereby spur innovative thinking. With minor adjustments in
wording, the TRIZ40 (n.d.) website replicates these 40 TRIZ Principles and they are included in
this report in Appendix III. Appendix IV includes examples of mistakeproofing practices and
the description of each practice also mentions which TRIZ Principle appears to have been
applied. For more detail, however, please refer to Altshuller (1999) and the TRIZ40 (n.d.)
website.
Innovation using the 40 TRIZ Principles (Figure 9) is a four-step process. It requires (1) an
expression of concern (earlier in the report, a distinction was made between concern and
problem), (2) abstraction to a more conceptual level, (3) followed by the application of a
Principle, and (4) then specialization to formulate a countermeasure (solution).
Figure 9: Prism of TRIZ Problem Solving Solutions (Oxford Creativity,
(upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Prism_of_TRIZ_Oxford_Creativity.png/
640px-Prism_of_TRIZ_Oxford_Creativity.png)

24
To expand on the 40 TRIZ Principles, consider items 9 and 11 on the list in Appendix III:
9. Preliminary anti-action
9.1. If it will be necessary to do an action with both harmful and useful effects, this action
should be replaced with anti-actions to control harmful effects.
9.2. Create beforehand stresses in an object that will oppose known undesirable working
stresses later on.
and
11. Beforehand cushioning
11.1Prepare emergency means beforehand to compensate for the relatively low reliability of
an object.
These principles are commonly used when designing PPE such as steel-toed boots (steel to
cushion the blow of impact) and hard hats.
5. EXAMPLE APPLICATIONS OF PRINCIPLES OF
MISTAKEPROOFING AND TRIZ
With the 6 mistakeproofing principles presented in Section 3 and the mistakeproofing mind-set
explained, and 40 TRIZ Principles (Appendix III) available to rationalize innovations (in this
case, means for mistakeproofing), the best way to learn to apply it, is to study examples.
Appendix IV includes 30 examples of mistakeproofing practices in the architecture-engineering-
construction industry, selected to illustrate variety in application opportunities in design and
construction. They are labeled consecutively by the number shown in the lower-right corner.
The examples are ordered first by mistakeproofing principle, then by TRIZ principle. The box in
the upper-left of each illustration designates, based on the color codes shown in Figure 1, which
of 6 mistakeproofing principles the example is to illustrate. The box next to it, with blue text
designates which of 40 TRIZ principles (all listed in Appendix III) the example is to illustrate.
One can also create a new means for mistakeproofing by combining the principles implemented
in different examples. One can imagine designing a nail gun with a contact sensor that also, like
SawStop (Example 30) gauges the conductivity of the surface it touches. The nail gun should fail
to engage upon contact with a person.
In fact, many examples may be used to illustrate multiple principles. We leave it to the reader to
expand on them further. The examples are intended to help readers practice their ability to see
and recognize mistakeproofing practices in their everyday environment and then leverage that
ability to create their own mistakeproofing applications.

25
6. RESEARCH FINDINGS AND CONCLUSIONS
The research led to the following findings:
1. The principles of mistakeproofing offer practical and useful application in the construction
industry. Their systematic pursuit is bound to help improve quality performance (including
safety and health performance by prevent hazards, incidents, and chronic pain altogether) in
the short- and long-term as it has across the board in other industries.
2. While perhaps not so obvious to the untrained eye, quite a few applications of
mistakeproofing already exist in the construction industry. The practice of mistakeproofing
construction needs to be made more visible. Documentation of existing practices will inspire
greater adoption of mistakeproofing.
3. While some mistakeproofing opportunities require investment in new product development,
many can be implemented at a minimal- if any cost.
4. The generation of new ideas on how to mistakeproof certain designs, tasks, or processes can
be supported by drawing on the principles of TRIZ (Theory of Inventive Problem Solving).
TRIZ takes a scientific approach to foster innovative thinking and offers methods that can be
taught. It should be considered for inclusion in a mistakeproofing curriculum.
5. The need to mistakeproof the design of everyday construction products (materials, tools,
assemblies, etc.) and processes (work methods) may seem obvious (or, upon reading this
report, hopefully will appear obvious in hindsight), but mistakeproofing is by no means a
common practice in the construction industry. Developing a mistakeproofing mindset starts
by raising awareness and empowering people to systematically experiment with making
changes in how work gets done on their projects, big or small, in pursuit of continuous
improvement. Training will be needed to foster a mistakeproofing mindset.
6. The six principles of mistakeproofing align to some degree with the five levels in OSHA’s
Hierarchy of Hazard Controls. They appear to be broader in their focus of application,
however, not so focused on safety and health, but rather addressing quality (which includes
concern for safety and health) at a more holistic level questions of production system design
and overall performance.
7. Further advancement of the use of mistakeproofing in construction will contribute to the
initiatives unfolding around Prevention through Design (PtD), Safety by Design (SbD), and
others that focus on improving the industry’s health and safety performance.

26
By explaining the goal to be achieved, defining the principles, and offering examples, this report
aimed to encourage broader awareness and use of this Lean Thinking method. Intentional and
purposeful use of mistakeproofing principles through their practical application will lead to
improved industry performance in construction, as it has in other industries.
7. ACKNOWLEDGMENTS
The authors of this report owe many thanks to everyone they spoke with and who hosted their
visits, for their time and willingness to contribute to this research by sharing ideas and examples
of mistakeproofing (only some of which made it into this report).
This research was funded by CPWR Small Study No. 16-3-PS. All support is gratefully
acknowledged. Any opinions, findings, and conclusions or recommendations expressed in this
report are those of the authors and do not necessarily reflect the views of anyone interviewed for
this study nor of their employer.

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APPENDIX I: GLOSSARY
This glossary of terms includes a number of definitions provided in Tommelein and Ballard
(2017), referred to as the “P2SL Glossary 2017.” In certain places, adjustments were made so
that those terms would be compatible with definitions used by OSHA (e.g., OSHA 2016).
5 WHYs, 5 Why analysis: Problem solving method based on asking Why? successively—at
least 5 times—in order to get beyond the symptoms of a problem that can be addressed with
a local countermeasure, to uncover the root cause of a problem that can be addressed by a
systemic, more lasting countermeasure. (P2SL Glossary 2017)
Reference: also see  Ohno (1988 p. 17)
40 TRIZ Principles: see  Appendix III.
ARIZ: Algorithm for Inventive Problem Solving, part of TRIZ developed by Altshuller (1984,
1997)
breakdown: Deviation from standard process or target outcome(s). Types of breakdowns:
• Incidents and close calls (near misses)
• Errors, defects, rework
• Broken promises, plan failures
A breakdown provides a learning opportunity because either (1) we did not properly perform
process A and need to learn how to, or (2) our knowledge regarding causality “IF A THEN
B” is inadequate. (P2SL Glossary 2017)
close call, near miss: Incident that could have—if circumstances had been slightly different—
resulted in human harm, but did not.
Condition of Satisfaction (COS): Directive (proactive: for steering) and criterion (reactive: for
judging), imposed by the entity initiating a process (usually the customer) that specify (to the
performer of that process) how success of the outcome will be gauged.
What will make a customer satisfied with the service or product received. (P2SL Glossary
2017)
COS  see Condition of Satisfaction (COS)

28
defect: An output that does not conform to a Condition of Satisfaction (COS) or specification;
not to standard; not of quality.
detection [mistakeproofing]: principle of mistakeproofing aimed at helping people recognize
that a mistake has occurred, e.g., by providing sensory feedback, so that they can promptly
correct the situation.
DfS: see  Safety by Design (SbD)
elimination1
[hierarchy of controls]: Change in process or workplace condition that removes the
hazard or ensures that no person can be exposed to a hazard under any foreseeable
circumstances (after OSHA 2016).
elimination2
[mistakeproofing]: principle of mistakeproofing aimed at redesigning the product
or process so that the task where people may make mistakes or incidents may occur is no
longer needed.
error: see  mistake
errorproofing: see  mistakeproofing
facilitation [mistakeproofing]: principle of mistakeproofing that aims at making tasks easier to
perform and helping people make distinctions in a situation or artifact that are relevant to the
proper execution of their task, by providing sensory input.
fail safing: see  mistakeproofing
Failure Modes and Effects Analysis (FMEA): “Failure modes and effects analysis (FMEA) is a
step-by-step approach for identifying all possible failures in a design, a manufacturing or
assembly process, or a product or service. (ASQ 2017).”
FMEA  see Failure Modes and Effects Analysis
hazard: Situation where an event may occur that causes human harm.
hazard analysis: Technique that focuses on tasks as a way to identify hazards before they occur.
It focuses on the relationships among the worker, the task, the tools, and the work
environment (after OSHA 2016).
Hierarchy of Hazard Controls: System for selecting and implementing the most effective
control solutions for workplace hazards that includes:
1. Elimination
2. Substitution
3. Engineering controls
4. Administrative controls
5. Personal protective equipment
This is referred to as a hierarchy because they should be considered in the order presented.
Controls at the top of the hierarchy are potentially more effective and more protective than
those lower in the hierarchy (OSHA 2016).
Reference: Peterson (1973)
human harm: Death, injury, or illness.

29
illness: Human harm caused by, e.g., skin diseases or disorders, respiratory conditions,
poisoning, and hearing loss (OSHA categories in Zaidman 2006)
Reference: Zaidman (2006)
In contrast to  injury
incident: Occurrence of an event that results in a fatality, injury, illness, or close call (sometimes
called "near misses"), in which a person might have been hurt if the circumstances had been
slightly different.
injury: Wound or damage to the body resulting from an event in the (work) environment.
Examples are a cut, abrasion, fracture, or burn. Sprain and strain injuries to muscles, joints,
and connective tissues are classified as injuries when they result from a slip, trip, fall, or
other similar incidents (after Zaidman 2006).
job hazard analysis: see  hazard analysis.
mistake, error: Inadvertent human action that may lead to a defect in a process or product, or
harm to a person.
mistakeproofing, poka yoke, errorproofing, fail-safing (P2SL Glossary 2017): Designing
products or processes to eliminate (or at least to reduce) the probability or impact of mistakes
and defects in use or execution. Mistakeproofing is based on six principles:
1. Elimination (akin to elimination as defined in Hierarchy of Controls)
2. Prevention
3. Replacement or substitution (akin to substitution as defined in Hierarchy of Controls)
4. Facilitation
5. Detection
6. Mitigation
Reference: Shingo (1986)
mitigation [mistakeproofing]: principle of mistakeproofing aimed at alleviating or minimizing
the impact of a mistake or incident that has occurred.
near miss: see  close call.
poka yoke: see  mistakeproofing
PPE: personal protection equipment
Prevention through Design (PtD): Anticipating and “designing out” (preventing the occurrence
of) potential occupational safety and health hazards that may arise as a result of people
engaging in processes to make products (e.g., organizing work using work structuring or
operation design) or using products-as-designed (e.g., materials, assemblies, equipment,
tools) (P2SL Glossary 2017)
References: NIOSH (2014), Schulte et al. (2008), designforconstructionsafety.org
Related see  mistakeproofing and Safety by Design (SbD)
process capability: Probability distribution describing the variation in a property of the output of
a process (e.g., the geometry of the material produced) under normal operating conditions.
This definition pertaining to geometry equally applies to any material, resource, or process
property such as duration, temperature, impact strength, etc. (P2SL Glossary 2017)
PtD  see Prevention through Design

30
quality: Meeting requirements. “Consistently producing a product (outcome) that meets
customers’ expectations and that is fit for the purpose intended. (Lichtig 2011)” (P2SL
Glossary 2017)
root cause analysis: A collective term that describes a wide range of approaches, tools, and
techniques used to uncover causes of problems (OSHA 2016).
safe, safety: Not harmful. (P2SL Glossary 2017)
Safety by Design (SbD): Practice that encourages product and process designers to “design out”
during design development what may be health and safety risks to makers and users of their
design. It supports the view that design affects, not only quality, scope, and cost, but also
safety (after Wikipedia 2016). (after P2SL Glossary 2017)
In the context of mistakeproofing, SbD follows two principles, elimination and
substitution.
Reference: Wikipedia (2016-05-14) https://en.wikipedia.org/wiki/Safety_by_design (17 JAN 2017)
Related  see Prevention through Design (PtD)
SbD  see Safety by Design
self-inspection: Process whereby the performer of a task confirms that the hand-off produced
conforms to requirements and all known purposes including the purpose expressed in the
Conditions of Satisfaction (COS) of the immediate and ultimate customers. This eliminates
the defects against known requirements and it eliminates the defects that are relevant to the
next customers, though possibly not all defects that may affect customers further
downstream. (P2SL Glossary 2017)
In contrast to  successive inspection
Ref.: Shingo, S. (1986). Zero Quality Control: Source Inspection and the Poka-Yoke System. Taylor&Francis.
small win: Related to continuous improvement, recognition that any gain (win) is a gain (win)
and therefore worth pursuing. More importantly, alertness to small wins sharpens people’s
skills at finding improvement opportunities in general. (P2SL Glossary 2017)
References: Akers (2011), Amabile and Kramer (2011)
source inspection  see self-inspection
standard: An agreed-upon reference or baseline from which deviation is observed and
measured. Any standard is implied to be a current-best standard that can be improved upon
and replaced by a better standard.
standard(ized) work: Agreed-upon process for performing work, used repeatedly, and serving
as the baseline from which to measure improvements.
substitution [hierarchy of controls]: The replacement of a toxic or hazardous material (or the
equipment or processes used with them) with one that is less harmful. (OSHA 2016)
substitution2
[mistakeproofing]: principle of mistakeproofing aimed at identifying tasks where
people make mistakes or incidents occur, and then replacing them with tasks that are less
error- and incident-prone (e.g., a less hazardous one).

31
successive inspection: Inspection performed by the immediate customer of a process, principally
focused on the inspector’s own Conditions of Satisfaction (COS). This may include technical
inspectors who take into account all quality conditions. (P2SL Glossary 2017)
In contrast to  self-inspection
Reference: Shingo (1986).
TRIZ: Theory of Inventive Problem Solving, developed by Altshuller (1984, 1997, 1999)

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APPENDIX II: REFERENCES AND SELECTED BIBLIOGRAPHY
Akers, P.A. (2011). 2 Second Lean: How to Grow People and Build a Fun Lean Culture.
FastCap LLC, 176 pp., www.2secondlean.com
Altshuller, G.S. (1984). Creativity as an Exact Science. The Theory of the Solutions of Inventive
Problems. Translated from Russian by A. Williams, Studies in Cybernetics: 5, Gordon and
Breach Sci. Pubs., NY, 319 pp.
Altshuller, G. (1997). 40 Principles: TRIZ Keys to Technical Innovation. Translated from
Russian by L. Shulyak and S. Rodman, Worchester, MA: Technical Innovation Center. 141
pp.
Altshuller, G. (1999). The Innovation Algorithm – TRIZ Systematic Innovation and Technical
Creativity. Translated from Russian by L. Shulyak and S. Rodman, Worchester, MA:
Technical Innovation Center. 312 pp.
Amabile, T. and Kramer, S. J. (2011). “The Power of Small Wins.” Harvard Business Review.
May.
ASQ (2017). Failure Modes and Effects Analysis (FMEA). http://asq.org/learn-about-
quality/process-analysis-tools/overview/fmea.html
Ballard, G. (2000). The Last Planner System of Production Control. PhD Dissertation,
University of Birmingham, UK.
Ballard, G., Tommelein, I., Koskela, L., and Howell, G. (2002). “Lean Construction Tools and
Techniques.” Chapter 15 in Rick Best and Gerard de Valence (editors, 2002). Design and
Construction: Building in Value. Butterworth-Heinemann, Elsevier Science Ltd, pp. 227-255.
Baudin, M. (2001). “When to Use Statistics, One-piece Flor, or Mistake-Proofing to Improve
Quality.” Manufacturing Management & Technology Institute (MMTI), Palo Alto, CA, 10
pp.
BMGI (2016). “Mistake Proofing Techniques.” bmgi.org/sites/bmgi.org/files/Mistake_
Proofing_Techniques.pdf (June 16, 2016).
Bodek, N. (1986). Page vii of Publisher’s Preface to Shingo (1986).
Bureau of Labor Statistics (BLS) (2013). “Numbers of Nonfatal Occupational Injuries and
Illnesses by Case Type and Ownership, Selected Industries 2012.”
www.bls.gov/news.release/osh.t02.htm (Nov. 20, 2013).
Bureau of Labor Statistics (BLS) (2016). “Industries at a Glance: Work-related Fatalities,
Injuries, and Illnesses 2014.” www.bls.gov/iag/tgs/iag23.htm (May 10, 2016).
Cerit, B., Küçükyazıcı, G., and Şener, D. (2014). “TRIZ: Theory of Inventive Problem Solving
and Comparison of TRIZ with the other Problem Solving Techniques.” Balkan J. of Electr.
and Computer Engineering, 2(2) 66-74.
Dekker, S. (2004). Ten questions about human error: A new view of human factors and system
safety. CRC Press.
Dekker, S. (2006). The field guide to human error. Bedford, UK: Cranfield Univ. Press.
Dekker, S. (2012). Just culture: Balancing safety and accountability. Ashgate Publishing, Ltd.

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Dekker, S. (2014). The Field Guide to Understanding 'Human Error.' Ashgate Publishing, Ltd.
dos Santos, A. and Powell, J. (1999). “Potential of poka-yoke devices to reduce variability in
construction.” Proc. 7th
Ann. Conf. Int’l. Group for Lean Constr., Berkeley, CA, pp. 51-62.
dos Santos, A., Powell, J., and Formoso, C.T. (1999). “Evaluation of Current Use of Production
Management Principles in Construction Practice.” Proc. 7th
Ann. Conf. Int’l. Group Lean
Constr., Berkeley, CA, pp. 73-84.
dos Santos, A., Powell, J., Sharp, J., and Formoso, C.T. (1998). “Principle of transparency
applied in construction.” Proc. 6th
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APPENDIX III: 40 TRIZ PRINCIPLES
Altshuller (1999 pp. 287-289) identified a set of 40 TRIZ Principles that can be applied to
resolve contradictions and thereby spur innovative thinking. With minor adjustments in wording,
the TRIZ40 (n.d.) website replicates these 40 TRIZ Principles. The site furthermore offers
examples from various domains for each principle and mentions which contradictions may be
solved by which principle(s) by relating them in matrices akin to Altshuller’s (1999 pp. 281-285)
Contradictions Matrix.
As Appendix IV includes examples of mistakeproofing practices and the description of each
practice also mentions which TRIZ principle appears to have been applied, those 40 TRIZ
principles are listed next. For more detail, however, please refer to Altshuller (1999) and the
TRIZ40 (n.d.) website.
1. Segmentation
1.1. Divide an object into independent parts.
1.2. Make an object easy to disassemble.
1.3. Increase the degree of fragmentation or segmentation.
2. Taking out
2.1. Separate an interfering part or property from an object, or single out the only necessary
part (or property) of an object.
3. Local quality
3.1. Change an object's structure from uniform to non-uniform, change an external
environment (or external influence) from uniform to non-uniform.
3.2. Make each part of an object function in conditions most suitable for its operation.
3.3. Make each part of an object fulfill a different and useful function.
4. Asymmetry
4.1. Change the shape of an object from symmetrical to asymmetrical.
4.2. If an object is asymmetrical, increase its degree of asymmetry.
5. Merging
5.1. Bring closer together (or merge) identical or similar objects, assemble identical or
similar parts to perform parallel operations.
5.2. Make operations contiguous or parallel; bring them together in time.
6. Universality
6.1. Make a part or object perform multiple functions; eliminate the need for other parts.
7. Nested doll
7.1. Place one object inside another; place each object, in turn, inside the other.
7.2. Make one part pass through a cavity in the other.

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8. Anti-weight
8.1. To compensate for the weight of an object, merge it with other objects that provide lift.
8.2. To compensate for the weight of an object, make it interact with the environment (e.g.
use aerodynamic, hydrodynamic, buoyancy and other forces).
9. Preliminary anti-action
9.1. If it will be necessary to do an action with both harmful and useful effects, this action
should be replaced with anti-actions to control harmful effects.
9.2. Create beforehand stresses in an object that will oppose known undesirable working
stresses later on.
10. Preliminary action
10.1. Perform, before it is needed, the required change of an object (either fully or partially).
10.2. Pre-arrange objects such that they can come into action from the most convenient
place and without losing time for their delivery.
11. Beforehand cushioning
11.1. Prepare emergency means beforehand to compensate for the relatively low reliability
of an object.
12. Equipotentiality
12.1. Change the condition of the work in such a way that it will not require lifting or
lowering an object (Altshuler 1999 p.287)
13. Do it in reverse (Altshuler 1999 p.287), the other way around
13.1. Invert the action(s) used to solve the problem (e.g. instead of cooling an object, heat
it).
13.2. Make movable parts (or the external environment) fixed, and fixed parts movable.
13.3. Turn the object (or process) 'upside down'.
14. Spheroidality – Curvature
14.1. Instead of using rectilinear parts, surfaces, or forms, use curvilinear ones; move from
flat surfaces to spherical ones; from parts shaped as a cube (parallelepiped) to ball-
shaped structures.
14.2. Use rollers, balls, spirals, domes.
14.3. Go from linear to rotary motion, use centrifugal forces.
15. Dynamicity / Dynamics
15.1. Allow (or design) the characteristics of an object, external environment, or process to
change to be optimal or to find an optimal operating condition.
15.2. Divide an object into parts capable of movement relative to each other.
15.3. If an object (or process) is rigid or inflexible, make it movable or adaptive.
16. Partial or excessive actions
16.1. If 100 percent of an object is hard to achieve using a given solution method then, by
using 'slightly less' or 'slightly more' of the same method, the problem may be
considerably easier to solve.

39
17. Another dimension
17.1. To move an object in two- or three-dimensional space.
17.2. Use a multi-story arrangement of objects instead of a single-story arrangement.
17.3. Tilt or re-orient the object, lay it on its side.
17.4. Use 'another side' of a given area.
18. Mechanical vibration
18.1. Cause an object to oscillate or vibrate.
18.2. Increase its frequency (even up to the ultrasonic).
18.3. Use an object's resonant frequency.
18.4. Use piezoelectric vibrators instead of mechanical ones.
18.5. Use combined ultrasonic and electromagnetic field oscillations.
19. Periodic action
19.1. Instead of continuous action, use periodic or pulsating actions.
19.2. If an action is already periodic, change the periodic magnitude or frequency.
19.3. Use pauses between impulses to perform a different action.
20. Continuity of useful action
20.1. Carry on work continuously; make all parts of an object work at full load, all the time.
20.2. Eliminate all idle or intermittent actions or work.
21. Skipping
21.1. Conduct a process, or certain stages (e.g. destructible, harmful or hazardous
operations) at high speed.
22. *Blessing in disguise* or *Turn Lemons into Lemonade*
22.1. Use harmful factors (particularly, harmful effects of the environment or surroundings)
to achieve a positive effect.
22.2. Eliminate the primary harmful action by adding it to another harmful action to resolve
the problem.
22.3. Amplify a harmful factor to such a degree that it is no longer harmful.
23. Feedback
23.1. Introduce feedback (referring back, cross-checking) to improve a process or action.
23.2. If feedback is already used, change its magnitude or influence.
24. Intermediary
24.1. Use an intermediary carrier article or intermediary process.
24.2. Merge one object temporarily with another (which can be easily removed).
25. Self-service
25.1. Make an object serve itself by performing auxiliary helpful functions.
25.2. Use waste resources, energy, or substances.
26. Copying
26.1. Instead of an unavailable, expensive, fragile object, use simpler and inexpensive
copies.
26.2. Replace an object, or process with optical copies.
26.3. If visible optical copies are already used, move to infrared or ultraviolet copies.

40
27. Cheap short-living objects
27.1. Replace an inexpensive object with a multiple of inexpensive objects, comprising
certain qualities (such as service life, for instance).
28. Mechanics substitution
28.1. Replace a mechanical means with a sensory (optical, acoustic, taste, or smell) means.
28.2. Use electric, magnetic and electromagnetic fields to interact with the object.
28.3. Change from static to movable fields, from unstructured fields to those having
structure.
28.4. Use fields in conjunction with field-activated (e.g., ferromagnetic) particles.
29. Pneumatics and hydraulics
29.1. Use gas and liquid parts of an object instead of solid parts (e.g., inflatable, filled with
liquids, air cushion, hydrostatic, hydro-reactive).
30. Flexible shells and thin films
30.1. Use flexible shells and thin films instead of three dimensional structures
30.2. Isolate the object from the external environment using flexible shells and thin films.
31. Porous materials
31.1. Make an object porous or add porous elements (inserts, coatings, etc.).
31.2. If an object is already porous, use the pores to introduce a useful substance or function.
32. Color changes
32.1. Change the color of an object or its external environment.
32.2. Change the transparency of an object or its external environment.
33. Homogeneity
33.1. Make objects interacting with a given object of the same material (or material with
identical properties).
34. Discarding and recovering
34.1. Make portions of an object that have fulfilled their functions go away (discard by
dissolving, evaporating, etc.) or modify these directly during operation.
34.2. Conversely, restore consumable parts of an object directly in operation.
35. Parameter changes
35.1. Change an object's physical state (e.g., to a gas, liquid, or solid.)
35.2. Change the concentration or consistency.
35.3. Change the degree of flexibility.
35.4. Change the temperature.
36. Phase transitions
36.1. Use phenomena occurring during phase transitions (e.g., volume changes, loss or
absorption of heat, etc.).
37. Thermal expansion
37.1. Use thermal expansion (or contraction) of materials.
37.2. If thermal expansion is being used, use multiple materials with different coefficients of
thermal expansion.

41
38. Strong oxidants
38.1. Replace common air with oxygen-enriched air.
38.2. Replace enriched air with pure oxygen.
38.3. Expose air or oxygen to ionizing radiation.
38.4. Use ionized oxygen.
38.5. Replace ozonized (or ionized) oxygen with ozone.
39. Inert environment atmosphere
39.1. Replace a normal environment with an inert one.
39.2. Add neutral parts, or inert additives to an object.
40. Composite materials
40.1. Change from uniform to composite (multiple) materials.

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APPENDIX IV: CATALOG WITH MISTAKEPROOFING EXAMPLES
The following pages present 30 examples of mistakeproofing practices in the architecture-
engineering-construction industry, selected to illustrate variety in application opportunities of
mistakeproofing in design and construction. The examples are ordered first by mistakeproofing
principle, then by TRIZ principle. The box in the upper-left of each slide designates, based on
the color codes shown in Figure 1 (this figure appeared earlier in the report but is copied below),
which of 6 mistakeproofing principles the example is to illustrate. The box next to it, with blue
text designates which of 40 TRIZ principles (all listed in Appendix III) the example is to
illustrate.
In fact, many examples may be used to illustrate multiple principles. We leave it to the reader to
expand on them further. The examples are intended to help readers practice their ability to see
and recognize mistakeproofing practices in their everyday environment and then leverage that
ability to create their own mistakeproofing applications.
Figure 1: Color Code for Each of Six Mistakeproofing Principles

Cordless Power Tool
CONCERN:
1. The electrical cord on a power tool limits the
worker’s working range.
2. The cord attached to the tool and any
extension cords may get tangled or damaged
in use, and create a tripping hazard.
COUNTERMEASURE: Eliminate cord and tripping
hazard by using batteries to supply electricity to
power tools.
LIMITATION: Battery-powered tools tend to have
less power and limited in capacity.
Two nearly identical circular saws.
Photo Credit: Tim Carter - www.askthebuilder.com/which-circular-saw-should-i-buy/ 1
TRIZ Principle 2 Taking Out: Separate an
interfering part or property from an object,
or single out the only necessary part (or
property) of an object.
Connection Plug
CONCERN:
1. Electrical wires may get connected wrongly.
2. Electricians must work at elevation to wire linear
light fixtures.
COUNTERMEASURE:
In a shop environment, install clips to end the wiring
on each fixture. Put on correctly, these clips can snap
together in only one way (asymmetry) so that the
wires will always be connected correctly.
The electrician’s installation work at elevation takes
less time.
Connect plug and wiring of linear light fixtures (Source: Finelite (2008). Estimator and Contractor Guide.
Available online at http://www.finelite.com/contractor/ContractorGd_m.pdf visited 22 April. 2
TRIZ Principle 4 Asymmetry:
4.1 Change the shape of an object
from symmetrical to asymmetrical.
43

Manhole Cover
CONCERN: The cover for an opening that is
rectangular (e.g., a ground excavation), can be
turned sideways and fall into the opening.
People working underneath inside the opening
would be in harm’s way.
COUNTERMEASURE: A manhole cover is round
because a round cover cannot fall through a
circular opening of at least the same diameter,
no matter how it is positioned.
Manhole cover (McCarthy (2015-01-07) “Why Are Manhole Covers Round?” mentalfloss.com/article/60929/why-are-
manhole-covers-round 19 OCT 2016).
TRIZ Principle 14 Spheroidality (Curvature):
Instead of using rectilinear parts, surfaces, or
forms, use curvilinear ones…
3
Lock with Electronic Key
CONCERN: losing a key
COUNTERMEASURE: an electronic lock unlocks by
inputting a (memorized) code using a keypad, by
reading a person’s iris, or by reading their
fingerprint.
Lock with keypad or sensor
(www.wired.com/2013/06/smart-locks/ visited by AlChaer on 10/30/2017) 4
TRIZ Principle 6 Universality:
6.1 Make a part or object perform
multiple functions; eliminate the
need for other parts.
44

Perimeter Guard
CONCERN: Workers may fall off the edge of the roof.
COUNTERMEASURE: A barrier along the perimeter will
hold back anyone coming too close.
A parapet (part of the permanent structure) that can
function as a perimeter guard eliminates the need to
provide temporary fall protection for construction and
maintenance activities on the roof thus reducing total
costs over the building life cycle.
Parapet - Figure from slide 52 in OSHA (2015). Design for Construction Safety. Powerpoint slides online at
https://designforconstructionsafety.files.wordpress.com/2017/10/dfcs_short-course-06_2015.pptx 5
Bolted Steel
Moment Resisting Frame
Hoist-in-place, bolted, moment-resisting frame
www.conxtech.com/conx-system/on-site-construction-services/ visited 11 FEB 2017
CONCERN: Workers must work at elevation to weld
connections during structural steel erection.
COUNTERMEASURE: Welded connections are replaced
by hoist-in-place beams that are then bolted together.
Worker can work while standing in basket.
Time to complete connections is reduced, so that the
time the worker has to work at elevation is reduced as
well.
6
TRIZ Principle 7 Nested Doll:
7.2 Make one part pass through
a cavity in the other.
45

Lockout-Tagout (LOTO)
CONCERN: Working with electricity can be dangerous: it
can harm a person (e.g., electrocution when touching a
live circuit) or ignite a fire. A worker can turn off the
breaker before starting any work, but then someone else
might turn it back on. The fact that anyone passing by
has access to the electrical breaker panel increases the
risk of electrocution.
COUNTERMEASURE: OSHA 1926.417 requires lockout-
tagout (LOTO) of circuits while any employee may be
exposed to contact with parts of fixed electric equipment
or circuits (US Department of Labor, n.d.).
A lock is placed on the door of the entire breaker panel
to prevent anyone other than the worker doing the work
from accessing the panel and accidently switching on
breakers that should not be switched on. By locking the
door, access to the breakers is prevented, and the safety
of the workers is enhanced.
Parts for Lockout (left) and Installed Panel Lockout (right) (Electrical Panel Lockout (2017) OSHA Compliant
Lockout Tagout Devices. http://www.panellockout.com/ visited by Bardaweel on 1 NOV 2017) 7
TRIZ Principle 9 Preliminary Anti-action:
9.1 If it will be necessary to do an action
with both harmful and useful effects, this
action should be replaced with anti-
actions to control harmful effects.
Weather-tight Roof
CONCERN: Metal roofs covering a large area will expand
and shrink significantly due to temperature changes. The
panels that make up the roof must allow for movement
while also guaranteeing weather-tightness.
Securing overlapping roof panels using a sheet metal
screw may cause a gap on one side (right-hand figure) ,
while squeezing out the sealant on the other side. Over
time, this may cause the roof to leak.
COUNTERMEASURE: (left and center figure) The sheet
metal was indented to accommodate a certain amount of
sealant, and embeds in the sealant were added (making
the composite) to guarantee a minimum thickness,
ensuring that enough sealant will be present to
guarantee performance.
A longer return leg eliminates the possibility of
movement (no gap) when the screw is screwed in.
Sealant and return leg guarantee roof performance
(Source: Butler manufacturing product literature;
http://www.butlermfg.com/images/level3_pages/re
turnleglink-large.jpg visited 5/23/06).
TRIZ Principle 40 Composite Materials:
Change from uniform to composite
(multiple) materials.
8
46

Towel Bar
Installation Template
CONCERN: Mounting a towel bar on a wall requires
accurate measurement of the spacing between
screws.
COUNTERMEASURE: The towel bar packaging can act
as a template to facilitate installation by identifying
the location of the drill holes, thereby eliminating the
need to measure the distance between screws and
then marking the location before drilling holes.
The template is held level and then taped to the wall.
The location of the 4 drill holes needed are illustrated
on the template without any additional work being
necessary.
Use of templates makes it significantly easier and
faster to complete the work.
Towel Bar Installation Template (Brittany (2015).
How to Install a Towel Bar Securely.
www.prettyhandygirl.com/how-to-install-towel-
bar-securely/ visited by Bardaweel on 1 NOV 2017) 9
Face-Mounted Tile
CONCERN:
• Achieve even spacing when mounting tile on a wall.
• Protect face of tile during transportation and
handling.
COUNTERMEASURE:
• Secure spacing before installation.
• Cover tile.
Glass mosaic tile comes glued face down on paper with
their back side exposed. They have ridges on the back to
allow adhesive to bond securely to an otherwise slick
glass surface.
First, tile adhesive is applied to the wall. Then the sheet
is pressed into the adhesive paper-side out. After the
adhesive and time have had time to bond securely, the
paper is sprayed with water until it slides from the face
of the tiles. Paper removed, the tiles can be grouted.
mosaicartsupply.com/paper-mesh-mosaic/
visited 10 March 2017
10
TRIZ Principle 10 Preliminary Action:
Perform, before it is needed, the
required change of an object (either
fully or partially).
47

Clamps to Rotate
Welded Steel Components
CONCERN:
• Welders must bend over and twist their bodies to
access connections to be welded.
• Weld material may run down due to gravity.
COUNTERMEASURE: “ConXtech is the first
manufacturing facility in the world to weld, in a
production environment, Hollow Structural Steel (HSS)
columns entirely in the horizontal position.”
• Welder works at comfortable height and can turn
by hand the column to the right position.
• Weld material is deposited horizontally.
ConXTech fabrication shop with rotating clamps
www.prweb.com/releases/conxtech/ladbs-approved/prweb10762433.htm
.
11
TRIZ Principle 12 Equipotentiality:
Change the condition of the work in
such a way that it will not require
lifting or lowering an object
Flexible Pipe
CONCERN: Neither the location where the plumbing
pipe comes out of the wall nor the location of the
fixture on the floor are very precise (installed within
some tolerance.
COUNTERMEASURE: Use a flexible pipe that bends to
suit site conditions.
Flexible water supply connector, Flex Pipe, or Flexi Hose
(Source: Picture by Iris D. Tommelein, Boston, MA, 2007) 12
TRIZ Principle 15 Dynamicity:
15.3 If an object (or process) is
rigid or inflexible, make it
movable or adaptive.
48

Paint Stencil
CONCERN: It is difficult to paint exactly what is
needed (e.g., a number) with sharp edges especially
when using spray paint.
COUNTERMEASURE: Stencils, painters’ tape, etc.
capture the overspray of paint, and get removed after
painting.
www.uline.com/Product/Detail/S-1963/Stencils/Brass-Stencils-Letters-and-Numbers-2?pricode=WB2005&gadtype=pla&id=S-
1963&gclid=EAIaIQobChMI9M-8-Yug2QIV27XACh1QrAizEAQYAyABEgJj7PD_BwE&gclsrc=aw.ds 13
TRIZ Principle16 Partial or Excessive Actions: If 100% of
an object is hard to achieve using a given solution method
then, by using 'slightly less' or 'slightly more' of the same
method, the problem may be considerably easier to solve.
Jig for Anchor Bolts
CONCERN: Light poles are secured to their concrete
foundation using four anchor bolts. The rods on which
they will be threaded must be aligned exactly or the
metal base of the pole will not fit onto them.
The rods must be lined up beforehand but may
accidentally move when concrete gets placed and
vibrated.
COUNTERMEASURE: Secure spacing before installation.
The jig secures the four rods in place relative to each
other.
“AJ Speedset is an adjustable jig that creates a simplified, time saving way to install ¾”, 1” or 1¼” anchor bolts in concrete for
area lighting.” www.rndproducts.com/products_aj.htm 14
TRIZ Principle 24 Intermediary:
24.1 Use an intermediary carrier
article or intermediary process.
49

Drawings and BIM Elements
CONCERN: On a black-and-white drawings, many wall
types may look alike. Symbols that denote each type
require a table lookup.
COUNTERMEASURE: Different colors designate
different wall types in design drawings to assist
estimators, plan reviewers, and builders with looking
up and “seeing” the differences.
Source: DPR Inc., Camino Medical Center Project
15
TRIZ Principle 32 Color changes:
32.1 Change the color of an
object or its external
environment.
Nail Heads
CONCERN: Using a nail that is too short will not result in
the required performance, and one that is too long may
protrude (become visible or penetrate another object).
COUNTERMEASURE: The heads of these pneumatic nails
have different colors to correspond to different lengths
and diameters. This makes it easy for workers to grab the
right nails (less likely they will confuse sizes), and
reorder the color they need.
It also makes it possible for workers and inspectors to see
and verify whether or not nails were installed according
to the design requirements.
Hawks, J. “Tool Review: Color-Coded Pneumatic Nails.” Fine Homebuilding Magazine reprinted on
http://www.taunton.com/finehomebuilding/pages/h00090.asp visited 5/23/06. 16
32.1 Change the color of an object
or its external environment.
50

Pipe Markers
CONCERN: Buildings include many piping systems, for
hot- and cold water supply, fire sprinklers, etc. The
proper pipe sections must be connected during
construction. The right valves must be opened and
closed while the facility is in use.
COUNTERMEASURE: Each pipe is identified by color
and with labels to indicate the system it supports
(e.g., per the ANSI/ASME 13.1 standard for
identification of pipe).
These colors help workers recognize the function of
each pipe, so they can clearly identify which one(s) to
work on, what valves to shut off, etc.
Pipe identified by color (blue: potable cold water,
green: hot water, and red: fire water)
www.safetysign.com/blog/brimar-is-coming-to-the-
ahr-expo/ visited by Briones on 11/02/2017
17
Color-Changing Paint
CONCERN: when using white paint to paint over a
white ceiling, it is hard to see which areas have
already been painted, so application may be uneven.
COUNTERMEASURE: Additives to the paint make the
white paint look pink for as long as it is wet. When it
dries, it gradually turns white.
Glidden® EZ Track Ceiling Paint - kk.org/cooltools/glidden-ceiling/
18
51

“Sterilize” an Area
CONCERN: When work is done overhead, objects may
fall down; they may strike people underneath or cause
damage when they hit something.
COUNTERMEASURE: Block off the area (“sterilize it”)
to show that no one is allowed to be underneath.
https://www.mprnews.org/story/2014/06/19/as-pipeline-production-soars-in-minnesota-critics-urge-focus-on-
safety#gallery Kraker, D. (19 JUN 2014). “As pipeline production soars in Minnesota, critics urge focus on safety.” 19
TRIZ Principle 39 Inert
Environment Atmosphere:
39.1 Replace a normal environment
with an inert one.
Mark Drill Hole Locations
CONCERN: Trades that follow the placement of a floor
slab with post-tensioned (PT) concrete may have to
drill into the slab to secure their work. It is hard to
know the exact location of the PT cable (depth and x-
y position in slab) but drilling into it is dangerous: it
could cause the cable to snap and jeopardize the
structure’s performance.
COUNTERMEASURE: Blue Bangers are inserts
positioned in-between PT cables and then nailed to
the slab formwork prior to placing concrete. They are
visible from underneath the slab when the formwork
has been stripped and mark spots where it is OK to
drill.
Source: Simpson Strongtie
20
TRIZ Principle 40 Composite
Materials: 40.1 Change from
uniform to composite
(multiple) materials.
52

Power Interrupter
for Drill
CONCERN: When drilling into a reinforced concrete
element, one can hit rebar, conduit, or other metal
embeds. Drilling into these may cause damage to the
element as well as the drill.
COUNTERMEASURE: A device called the PROTEK drill
interrupter helps detect metal in the concrete. As
soon as the drill bit makes contact with grounded
metal piping, conduit, reinforcement steel, etc. the
control loop is completed (closed) and the device
stops the electricity supply to the drill so that the
operator cannot continue to drill through the metal
object.
Drill Interrupter System (www.geotechsupply.com/protekiidrillinterrupter.aspx visited 18 OCT 2016)
21
TRIZ Principle 11 Beforehand
Cushioning: Prepare emergency means
beforehand to compensate for the
relatively low reliability of an object.
Rumble Strips
CONCERN: Distracted or sleepy drivers may veer off
the road or cross the centerline into the opposing
traffic lane.
COUNTERMEASURE: Rumble strips cause the vehicle to
make a loud noise (auditory feedback) that alerts the
driver, so that they can avoid running off the road or
colliding with other vehicles or obstacles.
www.rumblestrips.com/resources/research-and-publications/cyclists-and-rumble-strips/
visited by Briones on 11/02/2017 22
TRIZ Principle 18 Mechanical
Vibration: Cause an object to
oscillate or vibrate.
53

Crane Overload Switch
CONCERN: The load a hoist or crane can carry depends
on its rigging as well as the lift radius and thus boom
length. The crane capacity is lower when the lever
arm is greater.
COUNTERMEASURE: An overload switch indicates the
load carried by a hoisting device or crane.
Mechanical Overload Switch (vetec.dk/products/mechanical-overload-switch-crane-limit-switch-hoist-limit-
switch/ and vetec.dk/wp-content/uploads/2015/10/MECHANICAL-OVERLOAD-SWITCH.pdf visited 20 OCT 2017). 23
TRIZ Principle 23 Feedback:
23.1 Introduce feedback (referring
back, cross-checking) to improve a
process or action.
Tension Bolt
CONCERN: Structural bolts must have the proper
pretension in order to be functional. This tension is
achieved by torqueing the bolt however torque is not
a reliable indicator of tension.
COUNTERMEASURE: Squirter DTIs are compressible
washers that show when a bolt reaches its target
tension, independent of torque, by expressing orange-
colored material.
Myhrum, B. (2010). “Simple QA for Wind Turbine Bolts.” Windpower, online at
www.windpowerengineering.com/construction/simple-qa-for-wind-turbine-bolts/ 24
TRIZ Principle 23 Feedback:
23.1 Introduce feedback (referring
back, cross-checking) to improve a
process or action.
54

Electrical Fuse
CONCERN: When a load on a system exceeds its capacity, the
system will fail. When too much current flows through a
circuit, it can overheat and cause a fire.
COUNTERMEASURE: Intentionally create a weak spot in the
system so it will fail when the loads exceeds a threshold.
The weak spot– the fuse– will overheat and melt (“blow”)
when too much current (exceeding amperage of the fuse)
flows through the circuit. This interrupts the current before
more damage can occur.
By locating the fuse judiciously in the circuit, it will be easy
to locate the system failure and replace the fuse. One must
determine why the fuse blows and remedy the cause before
replacing the fuse with a new one, or it will also blow.
The illustration shows that the fuse gives a visual indication
of its demise (text after Chris 2015).
Fuse before (top) and after it has blown (bottom); this fuse shown is for single use. Other kinds of fuses may be
reset and reused. Source: Chris (2015). “Electrical Fuses | The Home Depot Community.” The Home Depot, 24
Nov., community.homedepot.com/howto/DiscussionDetail/Fuses-90650000000CeU9) 25
TRIZ Principle 3 Local Quality:
3.1 Change an object's structure
from uniform to non-uniform.
Toeboard on Scaffold
CONCERN: A worker on a scaffold may accidentally
push over an object staged on the platform (e.g., a
bucket) and strike a worker passing underneath or
cause damage.
COUNTERMEASURE: OSHA (2010) requires workers on a
scaffold 10 feet or higher to place toe boards at the
platform edges to mitigate the chance of kicking over
objects.
This reduces the chance of an object falling down; it
does not fully prevent it from happening.
Toeboard on Scaffold
www.contractors-solutions.net/Toe-Board-Bracket-for-Utility-Scaffolding.aspx visited by AlChaer on 10/30/2017
OSHA (2010) https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=27335 visited on
10/30/2017.
26
3.3 Make each part of an object
fulfill a different and useful
function.
55

“Dead Man” Cart Leg
CONCERN: Cart (as shown, loaded with 3,500 pounds
of glass) may tilt over or collapse due to wheel/caster
failure, and crush or kill a worker.
COUNTERMEASURE: Added a Dead man concept to the
4 corners of the fabricated cart to protect against
wheel/caster failure.
Wheeled cart with dead man legs
Stoker, I. and Stearns, L. (2017). “Harmon Glass Handling Kaizen-Report Out (Event Dates: 1/12 to 1/14).” Harmon, Inc.
Manufacturing Facility, Cincinnati, OH, 30 November 2017; Powerpoint slides provided by Chad Hoffmann, 23 pp. 27
3.3 Make each part of an object
fulfill a different and useful
function.
Worker Fall Protection
CONCERN: Workers can fall from heights.
COUNTERMEASURE: The g-link dual retractable system
allows 100% tie-off where one can move from one
anchor point to the next without disconnecting the
retractable. The bulk of the unit is attached to the
back of person’s harness and the system is constructed
of lightweight aluminum components, which reduces
worker fatigue.
Guardian G-Link Dual Retractable System
(www.fallprotectionpros.com/amfilerating/file/download/file_id/1317/ and
www.fallprotectionpros.com/guardian-g-link-dual-retractable-system-aluminum-rebar-11ft.html visited 18 OCT
2016)
28
56

Lanyard for Tools
CONCERN: “Dropping a tool while working at height
can have devastating consequences.”
COUNTERMEASURE: “Lanyards, which can be attached
to the operator's wrist, belt, harness or other suitable
tether site location,” prevent objects falling a great
distance.
www.utilityproducts.com/articles/print/volume-16/issue-2/readers-choice-awards/tools-supplies/utilities-can-
improve-productivity-and-safety-through-adoption-of-dedicated-tools-at-height-products.html 29
Table Saw Stop
CONCERN: People use their hands to push material
and cut it with the table saw. Their hand may get
caught by the blade.
Table saws have blade guards to reduce the likelihood
of a hand getting caught, but workers may remove
these guards as they find them to be impractical.
COUNTERMEASURE: “The SawStop saw detects contact
with skin. The blade carries a small electrical signal,
which the safety system continually monitors. When
skin contacts the blade, the signal changes because
the human body is conductive. The change to the
signal activates the safety system.”
www.sawstop.com
30
57

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