A RESEARCH SYNTHESIS ON THE INTERFACE
BETWEEN LEAN CONSTRUCTION AND
Eric I. Antillón
, Luis F. Alarcón
, Matthew R. Hallowell
, and Keith R.
Applying lean construction practices to safety management is a promising research
area and has been discussed by multiple authors. Some researchers propose that the
reduction of occupational hazards is a naturally occurring effect of the
implementation of lean practices. To further understand how lean practices affect
project safety performance, an interaction matrix between lean construction and safety
management practices was developed by performing a research synthesis and
validating the synthesis with structured interviews. The variables analyzed in this
interaction matrix were elements of the lean production system such as the last
planner system, autonomation, and standardization, and the most common safety
management practices such as planning and staffing for safety. The interface between
lean construction and safety management was systematically analyzed by assessing
the conclusions from previous investigations. The results indicate that there is a
significant amount of evidence of synergy between lean production practices and
safety management practices. For example, project-specific safety objectives can be
incorporated in the lookahead planning process, and autonomation could be directly
extended to worker involvement in such a way that workers can stop production
whenever they feel in danger, among others. This evidence, along with the results
obtained from the analysis of the interaction matrix, can also help to develop and
integrate future production and safety management models.
Lean Construction, Last Planner, Safety Management, Research Synthesis, Interaction
Research Assistant, Civil, Environmental and Architectural Engineering, University of Colorado,
428 UCB, Boulder, CO 80309-0428, Phone +1 303/735-0185, Fax 303/492-7317;
Professor, Department of Construction, Engineering and Management, Pontificia Universidad
Católica de Chile, Vicuña Mackenna 4860, Macúl, Campus San Joaquín, Edificio San Agustín, 3rd
Floor, 7820436, Santiago, Chile, Phone +56 2/3544345, Fax 2/3544806; email@example.com
Assistant Professor, Civil, Environmental and Architectural Engineering, University of Colorado,
428 UCB, Boulder, CO 80309-0428, Phone +1 303/492-7994, Fax 303/492-7317;
Associate Professor, Civil, Environmental and Architectural Engineering, University of Colorado,
428 UCB, Boulder, CO 80309-0428, Phone +1 303/735-4276, Fax 303/492-7317;
The construction industry has long been reputed for its high accident rates when
compared with other industries. It is one of the most dangerous industries worldwide
consistently accounting for the highest fatality rates. The International Labor
Organization (ILO) has made a conservative estimate claiming that at least 60,000
people are being fatally injured every year on building sites worldwide (ILO 2003).
Furthermore, in 2005 alone, the construction industry shared 1,243 (21.7 %) of the
total 5,734 work-related deaths from injuries in the US, while making up only 8% of
the overall workforce (CPWR 2008). Recent investigations have studied how safety
performance is affected by the implementation of lean practices and have shown that
they both improve the efficiency of production sites and result in favorable safety
outcomes (Thomassen et al. 2003; Saurin et al. 2004; Nahmens and Ikuma 2009;
Leino et al. 2010).
Minimizing waste in a production system is one of the cornerstones of lean
production. Improved safety performance, such as reduced injury and fatality rates, is
an example of waste reduction. Accidents result in reduced efficiency of a process,
resulting in non-value-adding events in a production system. Since lean principles aim
at reducing waste, it would be prudent to assume that the reduction of occupational
hazards is a naturally occurring outcome of the implementation of lean construction
The purpose of this paper is to discuss the relationship between lean construction
strategies and construction safety management practices. The underlying relationship
between the lean practices and safety has yet to be explored. Thus, the topic is still in
its infancy and needs to be addressed because it may help the industry to
simultaneously improve productivity and safety performance.
Lean production emerged from the ongoing development of alternatives to mass
production. Its primary foundation, however, has been accredited to the principles of
the Toyota Production System (TPS). The term ‘lean’ itself was so given in part to
counterpose the new production system to ‘mass’ production (Ballard 2000).
Koskela’s ground-breaking report challenged the construction industry to explore and
adopt the new concepts and techniques of this new production philosophy in order to
examine it as an alternative to the traditional production system for construction
(Koskela 1992). Based on the principles of lean production and its implementation in
the construction industry, the last planner system has been established as one of the
most effective lean construction tools (Ballard 2000).
HE LAST PLANNER SYSTEM
The Last Planner System (LPS) of production control has been established as an
effective methodology that improves efficiency by stabilizing the workflow in
construction sites. A concise summary and description of the most important elements
of LPS identified in this study is provided in Table 1.
Table 1: Elements of the Last Planner System
Element Description Key
The lookahead process is the second level of planning that
expresses what CAN be done after the master plan defines what
SHOULD be done.
Constraint analysis consists of determining the activities that
must be completed so that each assignment can be executed.
Once all constraints have been removed for each assignment,
the activities are then put into the workable backlog from which
the last planners can establish the weekly plan.
The last planner process establishes weekly commitments to
production (what WILL be done) based on the workable
backlogs produced in the lookahead process.
The Percent Plan Complete (PPC) consists on systematically
comparing the plans committed to the plans executed. This
measures the extent to which the front line supervisor’s
commitment (WILL) was realized and becomes the reliability
The root causes for nonconformance are tracked and analyzed
in order to develop a future plan and prevent it from happening
in the future, so that improvements can be made.
Based on the concepts of lean production several principles, methods, and tools were
developed revolving around the primary goal of eliminating all waste. The main
objective of TPS is to produce the products that the client demands with the best
quality, lowest cost, shortest lead time, best safety and high morale. In order to
accomplish such goals, Just-In-Time (JIT) delivery and Jidoka must be implemented
in the production process. JIT is a set of tools and techniques that allows a company
to produce and deliver products in small quantities, with short lead times, to meet
specific customer needs. JIT allows for “the delivery of the right items at the right
time in the right amount” (Liker 2004, p. 33). Jidoka, the Japanese term for
autonomation is a concept that consists on never letting a defect pass into the next
station within a production process and allowing machines or workers to stop
production whenever something unusual or defective is detected (Liker 2004). A
summary of the most common lean production practices is provided in Table 2.
Table 2: Lean Production Tools
Tool Description Key
Just-In-Time (JIT) consists on producing and delivering products
in small quantities, with short lead times, to meet specific
Autonomation consists on never letting a defect pass into the
next station allowing machines or workers to stop production
whenever something unusual is detected.
Production leveling reduces variability and inconsistency during
Standardization involves using stable, repeatable methods
everywhere to maintain the predictability, regular timing, and
regular output of processes.
Continuous improvement is the process of making continuous
internal, incremental, and iterative improvements to a process.
In 2008, the US construction industry had a fatality rate of 9.7 per 100,000 workers,
while the all-worker average was 3.6. Falls and electrocutions have been identified as
the leading causes of fatal injuries in the construction industry, whereas being struck
by an object, falls to lower levels, and over exertion in lifting remain the leading
causes of nonfatal injuries (CPWR 2008). The dynamic and unpredictable
construction tasks and environments, combined with the high production pressures
and workload, create a high likelihood of errors, which leads to accidents
(Mitropoulos et al. 2007). Safety performance in the construction industry has
improved in the past two decades, but it has reached a plateau, as recent statistics
suggest (ILO 2003; CPWR 2008).
CII released its report titled Zero Injury Techniques (CII 1993) which presented
the results from a safety study that had identified five strategies as the most successful
accident prevention techniques being used to achieve the “zero accident” objective.
This study was followed by a validation study (Hinze and Wilson 2000) to examine
changes made since its publication. The results of this study identified nine key
practices, or areas, that contribute to improved safety performance. The most
prevalent safety management practices that have been identified to analyzed in this
study. The key safety practices are described in Table 3.
Table 3: Safety Management Practices
Practice Description Key
Top managers must be actively involved in worker safety at the project
level to exert a strong influence on establishing the project safety
Staffing for safety implies that the right people, methods, and
resources are used to ensure safety on a construction project. The
appropriate staff ensures that safety needs are being satisfied.
Pre-project planning (longer-term) establishes and communicates
project-specific safety goals, plans, and policies before the
construction phase of the project. Pre-task planning (shorter-term),
such as JHA’s, ensures that tasks are performed with safety integrated
into the daily work routine.
Knowledge about performing tasks safely is vital to worker safety.
There are a variety of ways that this knowledge can be instilled, but
training is perhaps the most effective means. Training covers a wide
variety of topics, each of which may directly influence safety
performance when performing a given task.
This is essentially based on the view that workers are not just a
valuable resource to be protected but also a resource that can
contribute to achieving the goal of zero accidents.
In order to encourage safety performance, reinforcing such behavior is
a key element. If workers are evaluated and/or recognized for safe
behavior, then workers will seek to repeat that performance.
If a safety program is to be effective, it must involve the
subcontractors. They should be included in the orientation training, the
drug testing and the safety planning among other activities. All parties
must comply with the same safety guidelines including employees of
Accident investigations are important for identifying the root causes of
injuries in order to devise effective preventative measures. Many
companies include near misses also, indicating proactive measures.
EMERGING RESEARCH LINKING LEAN AND SAFETY
Nahmens and Ikuma (2009) showed that lean strategies encourage less material in the
work area, an orderly and clean workplace, and systematic workflow. Therefore, it
could be expected that standardizing, systematizing and regularizing production leads
to better safety. Poor safety is considered a form of waste because, from a lean
perspective, incidents that disrupt the flow of work or lead to injuries are waste
(Howell et al. 2002). Furthermore, injuries are costly not only in terms of human
suffering, but also in terms of worker compensation costs, lost time, lost productivity,
and higher employee turnover (Saurin et al. 2004). Safety should not be treated as a
separate subject from production, for it is an integral part of every production process;
safety depends on every action, material, and person used in a work process
(Nahmens and Ikuma 2009). Typical production planning decisions, which determine
what will be done, when, how and by whom, are the basis to establish preventive
measures (Saurin et al. 2004). As Leino et al. (2010) explains, safety shall be treated
as another one of the performance variables targeted by production management
along with cost, time, and quality. From a lean perspective, safety management is
about managing uncertainty given that it enables proactive planning, helping to
reduce workflow variability.
POINT OF DEPARTURE
It is evident that many of the new proposed approaches to construction safety within
the paradigm of lean need to be further assessed and are topics that are still in their
infancy. There is a lack of in-depth conceptual discussions on the interface between
lean construction and safety management. This will provide a basis for the discussion
of the strong correlation, which may or may not exist, between lean practices and
safety performance in construction. A framework that reiterates the interactions
between aspects of lean construction and safety management would enable an in-
depth conceptual discussion on this interface. The results from this can provide
evidence to promote and demonstrate the value of lean construction in construction
safety, yet another aspect of significant importance to construction projects, and can
also help to develop and integrate future production and safety management models.
A research methodology approach known as a research synthesis has been
implemented in this investigation. This approach closely examines previous studies
related to the topic at hand and it has been used to combine qualitative data related to
the interface between lean construction and safety management. This helped to
recognize and understand the interface between lean and safety. Empirical studies
were also inferred as supporting evidence for the interactions identified and how the
implementation of lean results in improved safety performance. This approach was
inspired by two similar studies to the one being undertaken (Martinez et al. 2009;
Sacks et al. 2010). Martinez et al. (2009) integrated the principles of sustainable
construction (green building) and lean construction to develop a “Green-Lean”
conceptual integration, while Sacks et al. (2010) similarly has analyzed the interaction
between lean construction and Building Information Modeling (BIM).
DATA COLLECTION AND ANALYSIS
Previous studies that have considered the interaction between lean construction and
safety were the focus of this study. The advantages of using these data was that it
enabled the possibility of obtaining not just the results from similar studies, but also
the language and words of the authors of these studies, which represents data that has
given a thoughtful input and a great deal of attention to compile. The data was
thoroughly collected in an iterative process to develop a fine framework, more
specifically an interaction matrix that encompasses across all of the possible
interactions between the lean construction tools and the most common safety
management practices (Table 4).
Table 4: Interaction of Lean Construction Tools and Safety Management Practices
Lean Construction Tools
Last Planner System Lean Production Tools
Backlog of Ready-Work
Last Planner Process
Root Cause Analysis
T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11
1 1 5 14 16 18
Staffing for Safety
2 3 6 11 11
Planning for Safety
2 3 4 6 11 15 16 20
12 17 18
7 8 9 13 17 19
Evaluation and Recognition
8 9 20
1 1 5 16
The extent of this study was rather to identify the most important and obvious
interactions, provide the supporting evidence from the research synthesis, and identify
the most significant interactions in the interaction matrix developed. Also, it is
important to note that this study provides the evidence for the potential synergy
between lean construction tools and the most common safety management practices.
The term tools has been implemented and used throughout the research to describe the
lean concepts and practices, given that these are the means to accomplish lean
construction. The interaction matrix initially identified a total set of 88 possible
interactions, from which 41 have supporting evidence, which are the interactions with
an index number noted in the matrix. These interactions with supporting evidence
were identified from 11 previous studies. Note that the research focuses mainly on
evidence available in literature.
DISCUSSION AND RESULTS
Table 4 displays an index number correlated with the interactions found in the
evidence, which identify the explanation of each interaction along with its supporting
evidence in a separate table. Due to the space limitations of this paper, the following
will discuss a few of the most salient interactions identified per tool (T1-T11) with the
safety management practices (S1-S8). For a complete discussion of the results of this
investigation, including a validation with an expert panel, and the other supporting
tables, see Antillón (2010). To maintain brevity, the details of the interviews are not
discussed in this paper. In the following text, the publications supporting the
statements made are provided in brackets at the end of the section. The reference
numbers correspond to the reference section at the end of the paper.
OOKAHEAD PROCESS - INTERMEDIATE PLANNING (T1)
Several of the strategies implemented by LPS can be easily extended to safety
planning, thus directly affecting the effectiveness of safety programs. One of the main
goals of the lookahead process is to shape the work flow sequence and rate. In terms
of pre-project planning for safety, this allows to establish more reliable project-
specific safety resources for a given time period during a project and thus staff for
safety accordingly.  
ONSTRAINT ANALYSIS (T2)
Constraint analyses determine what must be done for a given work assignment before
execution. By freeing any constraints identified, this allows to execute the assigned
task. A constraint analysis can systematically include safety constraints, such as job
hazard analyses, directly incorporating pre-task planning for safety as part of the
constraint analysis process. By performing safety constraint analyses similarly as part
of the production planning, risk can also be predicted better, which in turn allows
safety management to allocate, or staff, safety resources accordingly.   
ACKLOG OF READY-WORK (T3)
A workable backlog consists on having a list of the tasks that have gone through the
constraint analysis and are ready to be performed with the assurance that everything is
indeed workable. This idea can be easily extended to safety planning. A checklist of
soundness requirements that an assignment must go through is usually what
determines whether the assignment can be considered workable or not. Safety could
be included as part of these preconditions.  
AST PLANNER PROCESS - WEEKLY PLANNING (T4)
At this planning level, the actual workers, such as the foreman and other people
working on site (the last planners), play a significant role in planning. Worker
involvement is directly incorporated at this level to determine what can actually be
done (what will be done) in terms of the previously defined tasks with the workers’
perception of the work reliability. This is often referred to as a bottom-up perceptual
approach which can also be extended to safety by allowing the workers to determine
whether a task is reliable in terms of safety.   
The Percent Plan Complete (PPC) measurement consists on systematically comparing
the plans committed to the plans executed in a project. The safety planning and
control (SPC) model proposed by Saurin et al. (2004), which integrates safety
management to the production planning and control process extends this concept to
safety performance measurement in order to evaluate safety effectiveness. Using a
similar measurement for safety the percentage of safe work packages (PSW) carried
out is measured, which can directly evaluate worker’s safety performance. 
OOT CAUSE ANALYSIS (T6)
Investigating root causes for accidents or near misses, which may or may not be the
root causes for nonconformance with the assignments, safety management may
proactively devise effective preventive measures. When root cause analyses are
carried out, similarly causes for successful performance and safe work behavior,
rather than just causes for non-conformance might also influence workers perspective
on safety by recognizing “causes for conformance.”  
The delivery of the right safety resources, such as appropriate safety personnel and
personal protective equipment, at the right time, when risk levels are higher for
example, and in the right amount, can directly impact safety planning and staffing for
safety. Tools implementing the JIT concept help to forecast safety risks and therefore
management can allocate safety resources when and where they are needed, leveling
safety risk. Instead of allocating safety management efforts with the traditional “push”
approach, a more effective and less wasteful “pull” approach implementing JIT can
significantly impact planning and staffing for safety.  
Autonomation in itself applies the same concept that worker involvement strategies
for safety implement, that is, the use of the worker’s perception and input for
evaluating the aspects of safety programs. Therefore, autonomation can directly be
extended to worker involvement in such a way that workers can stop production
whenever they feel in danger. Proper safety training for workers to recognize such
hazards is also essential for autonomation to impact safety management. The
appropriate training for workers to make the right judgment when they feel in danger
would help in maintaining a desired level of risk or risk averseness.  
RODUCTION LEVELING (T9)
Through proper production leveling the appropriate resources can be matched to
production demands without exceeding the capabilities of the workers. This reduces
the chances of construction accidents while at the same time increasing productivity.
This impacts planning and staffing for safety strategies, and also shows
management’s commitment to try and improve safety performance while at the same
time reducing waste from a lean perspective.    
Standardization implies that procedures may reduce the degrees of freedom of
workers and define a space of safe performance where accidents will not happen. The
fact that upper level management standardizes safety related procedures
communicates the importance of working safely to all workers and improves project
safety culture. Similarly, procedures can emphasize the importance of proper safety
training, the incorporation of safety plans, expected safety outcomes for the workers
and subcontractor procurement based on safety records, among others. Another very
important aspect of safety management that can be standardized is accident
investigation, which may also include things such as near misses.  
ONTINUOUS IMPROVEMENT (T11)
Applying such strategy for many of the safety management practices with the goal of
achieving better results every time can significantly improve the effectiveness of
many of these safety efforts. It can be reasoned that in order for continuous
improvement to be implemented within a company in the first place, it must be
expressed from upper management. Associated tools that implement continuous
improvement, in addition to many of the other lean production tools, such as 5S and
visual management, foster a culture of continual improvement, which is essential for
the successful implementation of lean. Visual management can be extended for safety
purposes using things such as safety signs and boards displaying current accident
rates allowing all workers to identify issues, thus providing an opportunity to be
trained, the boundaries for safe performance and compare the expected safety
performance.   
The results demonstrate that several lean construction tools are related, directly or
indirectly, to some of the most common safety management practices that are
implemented in the industry today. The last planner system shows that, if applied
correctly and implementing all of its elements, the principles of lean construction can
be successfully accomplished. Furthermore, there are opportunities to include safety
management into the system and improve safety performance in the same way that the
last planner system improves production performance. In fact, it almost seems
unreasonable not to integrate or include safety with production planning, given its
importance in today’s industry. Along with cost, time, and quality, safety shall be
treated as another one of the performance variables targeted by production
management. The interaction matrix, along with the explanations of the interactions,
can be used to further investigate this specific issue, or help with the realization of the
potential synergy that is obviously present between lean construction and safety
The authors wish to thank the Center for Excellence in Production Management
(GEPUC), from the Pontifical Catholic University of Chile in Santiago, for their
assistance and collaboration during the data gathering phase of this study. A special
thanks to those who participated in the expert panel also, for the research validation
interviews of the study.
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