Contract Management Office
Contract Management & Operations Branch
The Constructability Review Process is intended to help improve the constructability and consequently the quality of a design. The resulting benefit is a cost-effective design that is biddable, buildable, and maintainable.
The requirements for Constructability Review are identified by the Ministry in an Expression of Interest (EOI) and Request for Proposal (RFP). A design assignment may include one or more Constructability Reviews during the development of design. The Constructability Review Process described below focuses on the following:
§ Formalised requirements;
§ Formalised approach;
§ Dedicated construction expertise and resources;
§ Reporting the outcome; and
§ Clear accountability for Implementing the findings / recommendations.
Constructability Review is a formalised process that utilizes a team with extensive construction knowledge to ensure that a design is buildable while also cost-effective, biddable, and maintainable, with reduced overruns and delays. A Constructability Review is to be conducted separate from and independent of the design team. The scope of Constructability Review is to be flexible to suit the individual project requirements.
Biddability Review is a review of contract documents to identify errors, omissions and conflicts in plans, specifications, quantities, work items/activities, operational constraints and appropriate basis of payment. Biddability Review is part of Constructability Review process.
At this time, Constructability Review process will be carried out for Detail Design only. In the future, the process may also be considered for Preliminary Design.
Internal Review: Definition
An Internal Review is managed by the successful service provider firm as identified in their EOI and RFP submissions to the Ministry and is undertaken by their team not involved with the design. The Review is conducted in a workshop format at the specified milestone completion(s) and will result in specific observations or recommendations for implementation in design. At this time, Internal Review may be considered at 50 and 80 Percent Stages of Design.
External Review: Definition
An External Review is conducted by one or more individual(s) listed in the Ministry’s Roster of External Reviewers for Constructability Review. The requirement for an External Review is identified by the ministry. A firm selects the individual(s) from the Ministry’s Roster, based the qualifications and expertise indicated. The firm identifies the individual(s) selected for External Review in their EOI and RFP submissions to the Ministry. An External Review is conducted at the schedule agreed and recommendations forwarded to the firm for implementation in design. At this time, External review is considered at 80 Percent Stage only.
The following types of Major Road Reconstruction/Widening projects with the level of detail listed below should be considered for Constructability Review:
- Highway Engineering: stage grade raises/cuts, utility locations, major reconstruction (interchange new or rehabilitation, adding/widening lanes);
- Bridges and Tunnels: temporary supports, temporary roadway protection, traffic staging over bridges, complex bridge foundations, launching of girders, both new and rehab;
- Environmental: environmental sensitivity and construction windows; and
- Traffic Staging: traffic staging on 400 series highways, QEW, and urban highways and bridges, high volume intersections/interchanges.
Only Internal Review is required at this time for assignments with a capital construction estimate of $10M - $20M.
Both Internal and External Reviews are typically required for assignments with a capital construction estimate greater than $20M. However complex and high risk assignments of lesser value may be assessed for Constructability Review, on case-by-case basis.
Minor road construction and resurfacing assignments generally will not require Constructability Review. No Constructability Review is required at this time for assignments with construction cost estimate less than $10M.
4.0 Frequency of Constructability Review
For large/complex assignments, the Constructability Review may be carried out at both 50 Percent and 80 Percent Stages. For other assignments, a Constructability Review may be conducted at 80 Percent Stage only.
50 Percent Completion Stage
- The Constructability Review (Internal) at 50 Percent Stage is conducted prior to an upcoming Milestone Review / other similar meeting with the ministry and the resulting Constructability Review recommendations are subsequently incorporated in design.
- Revised design (with Constructability Review recommendations incorporated) is sent to the Ministry prior to 60 Percent Milestone Review/Presentation meeting.
- Typical Review considerations include: the traffic staging, construction staging, construction method(s), environmental considerations, work area, access/egress details, construction schedule/working days, operational constraints, etc.
- The following type of information is provided for Constructability Review at 50 Percent Stage:
§ Scope of work details;
§ Up to date Drawings;
§ Operational constraints;
§ Foundation, pavement design, structural and other reports or draft reports;
§ Environmental reports;
§ Utility mapping;
§ Traffic recommendations including lane, ramp and access constraints that are proposed for the contract;
§ Draft critical path construction schedule including the production rates that were used; and
§ Construction Cost Estimates (current for the stage).
- At the Milestone Review meeting, the Service Provider reports on the Constructability Review carried out and the recommendations implemented.
80 Percent Completion Stage:
- Constructability Reviews (Internal and External) at 80 Percent Stage are conducted prior to the scheduled Design Complete / Presentation or other similar meeting. The resulting Constructability Review recommendations are subsequently incorporated in design.
- The Revised design package (with Constructability Review recommendations incorporated) is sent to the Ministry prior to Design Complete / Design Presentation or other such meeting.
- Typical Review considerations include: checking the details of design and staging layout, quantities, specifications, construction method(s), construction schedule, working day estimates, construction cost, work area, access/egress details, operational constraints, environmental considerations, worker safety and traffic safety, etc. as:
§ Reviewing contract documents to ensure that contract requirements are achievable in keeping with common construction methods / standards.
§ Addressing construction phasing and scheduling for completing construction activities, and incorporating incentive / disincentive features in the contract.
- Also includes Biddability Review, as:
§ Reviewing the plans / drawings, documents, quantities, estimates, specifications and payment items for completeness.
- The following type of information is provided for Constructability Review at 80 Percent Stage:
§ Scope of work details.
§ Final Drawings, Quantity Sheets and Documents.
§ Operational constraints.
§ Final foundation, pavement design, structural and other reports. (Note reports should include both factual data and recommendations)
§ Environmental reports.
§ Utility mapping.
§ Traffic recommendations. (Note lane, ramp and access constraints that will be included in the contract should be part of the contract documents.)
§ Critical path construction schedule including the production rates that were used.
§ Current Construction Cost Estimates (current for 80 Percent Stage).
- At the above Meeting, the Service Provider reports on the Constructability Review carried out and the recommendations implemented.
5.0 Staffing/Expertise Requirements
Depending on the scope of an assignment, typically, construction related expertise and knowledge in one or more of the following areas are required from the team members for Internal and External Review:
§ Traffic / Staging
§ Construction Supervision / Administration (biddability, construction claims, construction delays)
§ Bridge / Culvert Construction
§ Temporary / Permanent Drainage
§ Highway and Worker Safety
§ Pavement / Geotechnical
§ ATMS / Electrical
§ Maintenance (including maintainability, Maintenance access, etc.).
Depending upon the assignment, a minimum of five years of experience in Construction Supervision / Administration / Management or otherwise proven successful experience is required. The individual must have worked on at least three projects of similar size and scope in the above areas.
6.0 Procurement of Constructability Review Services
§ The Ministry project manager solicits a Detail Design assignment through EOI process and invites submissions from the qualified firms and identifies the following requirements:
- Number of Constructability Review(s) required in an assignment;
- Type of review(s) required for an assignment (i.e. External, Internal, or both); and
- Critical areas of expertise required for Constructability Review.
§ Three to five firms are short-listed based on the evaluations of the submissions received from the qualified service provider firms.
- A firm’s submission that does not meet the ministry’s Constructability Review requirements identified in EOI is disqualified and not considered.
§ The Ministry project manager invites proposal submissions from short-listed firms through a Request for Proposal (RFP) and identifies further details on Constructability Review required:
- Number of Constructability Review(s) required in an assignment;
- Critical areas of expertise required for Constructability Review;
- Follow up required for Constructability Review including implementation of the recommendations, signoff trail and reporting; and
- Any Reference Document(s).
§ The short-listed firms submit proposals to the ministry. A proposal covers the required Constructability Review(s), the team members and their expertise, workshop format, timelines and related details.
§ For the purposes of an Internal Review, generally one expert is required per critical area of work identified in an RFP. However if available, a firm may provide an individual with expertise in more than one area.
- A firm may also propose the team members in other related areas, as deemed necessary;
- A firm is to identify the Team Lead / Facilitator for the purposes of Internal Review. The Lead facilitates the Internal Review(s) carried out in workshop(s);
- The firm’s project manager for the assignment or any member of Design Team cannot be identified as a member of Constructability Review Team. The firm’s project manager will be available to provide any information required by Constructability Review Team related to the project and answer any questions;
- Ministry project manager or other Ministry staff are not to be part of Constructability Review team. The Ministry project manager may attend to observe the proceedings; and
- The firm provides the project schedule including the schedule for Constructability Review(s) such that all related follow up work occurs prior to the next scheduled Milestone Review Meeting or Design Complete / Design Presentation Meeting with the Ministry Staff.
§ Ministry evaluates the proposals submitted and awards the assignment through open and competitive bidding process.
- A proposal that does not meet the ministry’s Constructability Review requirements will be disqualified and not considered.
§ The successful firm proceeds with the design assignment including Constructability Review(s) as per agreed schedule.
- The firm retains the identified individuals to perform Internal and External Reviews as per the requirements details and schedules agreed.
7.0 Delivery of Constructability Review
Internal Review: Workshop
§ Constructability Review Workshop(s) as identified in the RFP and successful proposal are held at the date(s) agreed. Typically, a Workshop may be one to two days in duration, including a field visit as necessary. For complex project projects, a Workshop may take an additional day.
§ Prior to the Workshop, the design package/information as completed is forwarded to the lead of the Constructability Review team who circulates it to the team members for their individual reviews (for 80 % Review, also include the information on 50 % Review and any follow-up by conducted).
§ Each Constructability Review team member provides comments to the Team Lead by a due date prior to the workshop.
§ Constructability Review Lead consolidates the comments received and circulates those back to the Constructability Review team prior to the workshop
§ The Team Lead consolidates the comments on the design package / information, received from the individual team members, prior to the Workshop.
§ All members of Constructability Review team are to attend a scheduled Constructability Review Workshop for its full duration. Detail Design deliverables and any recommendations are collectively assessed and agreed.
§ During the workshop, the Service Provider Firm’s project manager provides an overview of the project including the work completed, site and other constraints, any external/regulatory requirements, follow-up work, completion schedule, any critical considerations, milestone or final deliverables, etc. Also, acts as a resource for Constructability Review as required (i.e. explain project background, design requirements, discuss issues, constraints and scoping, etc.).
The Workshop is to use the following type of formalized agenda:
- Workshop Opening;
- Overview by Service Provider Firm’s project manager;
- Field review of the site conditions, as necessary; and
- Discuss issues and consolidate collective observations and recommendations. Allow time to discuss all critical/pertinent issues in a project.
§ The Ministry project manager may attend the site visit and Constructability Review Workshop to observe only.
§ Lead for the Constructability Review team consolidates and forwards the collective observations / recommendations within one (1) week of completing the workshop, to the firm’s project manager for the design assignment, with a copy to the Ministry project manager.
§ External Review is required at 80 Percent Stage only. Review takes place at the date(s) agreed and close to Internal Review at 80 Percent Stage.
§ Design package/information as completed is forwarded to the External Reviewer (s) identified by the firm from the Ministry Roster.
§ If required, the External Reviewer(s) may request a meeting with the Service Provider firm’s project manager for an overview of the project and the work completed to date and other details as listed above.
§ External Reviewer(s) may conduct a field review of the site conditions, as required.
§ The Ministry Project Manager may attend the site visit or the meeting with the Service Provider firm’s project manager
External Review Format
- Overview Meeting with the Service Provider firm’s project manager, if required;
- Field review of the site conditions if required, by the External Reviewer; and
- External Reviewer(s) review design package/information and provide recommendations.
§ External Reviewer(s) provide(s) observations and recommendations within one week of completing a Review, to the firm’s project manager, with a copy to the Ministry project manager.
8.0 Constructability Review: Follow- up
§ The firm’s project manager assesses the recommendations received from Internal / Internal Reviews for application in design and responds back to the Ministry project manager, as to the actions taken on the Constructability Review findings, as:
- Recommendations accepted for application in design; and
- Recommendations that cannot be applied in design and any rationale/reasoning for not applying.
§ Ministry project manager may follow up and ask questions or clarification on the actions taken by the firm and may circulate the above correspondence/ documentation to the Ministry project team members for review.
§ At a subsequent Milestone Review Meeting with the ministry staff, the firm provides an overview of the Constructability Review(s) conducted and the recommendations implemented.
§ Prior to Design Complete Presentation Meeting, the Service Provider firm shall ensure that all work in the contract package is correctly included for payment. A contract package must be checked/verified and corrected for any errors and inconsistencies in plans, specifications, estimates and the requirements and details for all payment items. The Service Provider firm must submit with a contract package, a certification and sign-offs that the contract package and all details have been independently checked/verified and corrected for all payment items.
§ The Service Provider project manager submits a Constructability Review Report for the project prior to Design Complete Presentation Meeting. The Report is to include all Reviews carried out and the recommendations acted upon/implemented. The report must be submitted within four (4) weeks of completing the last Review.
The Service Provider firm’s project manager submits a Constructability Review Report for the project to the Ministry. This is to include all Reviews carried out and the recommendations acted upon / implemented. The report must be submitted within four (4) weeks of completing the last Review and one (1) week prior to Design Complete Presentation Meeting with the ministry staff.
Typical Constructability Review Report Format
LOCATION: DATE/LOCATION OF REVIEW:
During the Constructability Review Workshop, all comments will be recorded numerically, noting the person who identified the issue/comment, a description of the issue and its associated problems as well as any recommendations collectively made in the Workshop to mitigate the issue. The Document will also identify who on the Service Provider’s project team needs to take action to respond to this issue.
At the end of the Constructability Review Workshop, the Document is sent to the Service Provider’s project manager to take action. The Document is also copied to the ministry Project Manager who will distribute them to the project team.
Each item will require a designer response stating whether the Constructability Review recommendation is agreed to or if not then why. Once all action items have been responded to, the Document will be sent back to the ministry Project Manager for distribution to the entire project team.
2) Descriptions of project
3) List of documents available for review
4) Review Number (or % complete)
5) Documents Review: List all documents with issue dates reviewed (reports, approvals, correspondence, contract drawings / documents, environmental reports, utility plans, others)
Comment # 1
Drawing #’s or Document Page #’s
Service Provider project manager’s Response:
6) Review - drawings/documents
Drawing #’s or Document Page #’s
Service Provider Project Manager’s Response:
During the External Review, all comments will be recorded numerically including a description of the issue and its associated problems as well as any recommendations made to mitigate the issue.
At the end of an External Review, the observations/recommendations are sent to the Service Provider project manager to take action. A copy of the observations / recommendations is sent to the Ministry project manager who may distribute those to the project team.
Each item will require a designer response stating whether the Constructability Review recommendation is agreed to or if not then why. Once all action items have been responded to, the document will be sent back to the Ministry project manager for distribution to the entire project team.
1) External Reviewer Name(s)
2) Descriptions of project
3) List of documents available for review
4) Review Number: 80 % Complete
5) Documents Review: List all documents with issue dates reviewed (reports, approvals, correspondence, contract drawings / documents, environmental reports, utility plans, others)
Comment # 1
Drawing #’s or Document Page #’s
Service Provider Project Manager’s Response:
6) Review - drawings/documents
Comment # 1
Drawing #’s or Document Page #’s
Service Provider Project Manager’s Response:
[ شنبه بیست و یکم اردیبهشت 1392 ] [ 17:43 ] [ سعید رضا ]
Analyses of Systems Theory for Construction Accident Prevention
with Specific Reference to OSHA Accident Reports
To enhance workplace safety in the construction industry it is important to
understand interrelationships among safety risk factors associated with construction
accidents. This study incorporates the systems theory into Heinrich’s domino theory
to explore the interrelationships of risks and break the chain of accident causation.
Through both empirical and statistical analyses of 9,358 accidents which occurred in
the U.S. construction industry between 2002 and 2011, the study investigates
relationships between accidents and injury elements (e.g., injury type, part of body,
injury severity) and the nature of construction injuries by accident type. The study
then discusses relationships between accidents and risks, including worker behavior,
injury source, and environmental condition, and identifies key risk factors and risk
combinations causing accidents. The research outcomes will assist safety managers to
prioritize risks according to the likelihood of accident occurrence and injury
characteristics, and pay more attention to balancing significant risk relationships to
prevent accidents and achieve safer working environments.
Keywords: Construction safety, Accident prevention, Construction injury, Systems
theory, Domino theory
Accidents occur every day on a construction site. In 2010, there were a total
of four recorded injuries per 100 full-time construction workers in the United States’
(U.S.) construction industry (Bureau of Labor Statistics, 2012). Considering that the
industry employed 5.5 million workers during this time period, this injury rate
indicated 0.22 million workers experienced accidents during their work. This figure
includes 802 fatalities, which accounted for approximately 17% of the total number
of fatal injuries across all industries. In other words, every working day, more than
three workers failed to return home due to fatalities on a construction site.
To prevent accidents and improve workplace safety it is important to
understand how these accidents and injuries are generated. In one of the earliest
accident causation studies, Heinrich (1936) introduced the domino theory after
investigating 75,000 industry accident reports. According to Heinrich, there are five
sequential dominos contributing to a construction accident injury: (1) ancestry and
social environment, (2) fault of a person, (3) unsafe act and mechanical or physical
hazards, (4) accident, and (5) injury. These dominos fall over one another and create a
chain of events leading up to an accident causing worker injuries. More specifically,
he explained that accidents lead to injuries, and that these accidents are caused when
a worker commits unsafe acts or there are direct mechanical or physical hazards
related to the work. He suggested that the unsafe acts and conditions can be managed
by social and organizational supports such as safety training, and the number of
accidents can be reduced by understanding and eliminating unsafe acts (i.e., humanrelated
factors) and unsafe conditions (i.e., environment-related factors).
Based on this recognition, there have been considerable research studies
exploring the contributing human, environmental, and mechanical factors in
construction accidents. Hinze et al. (1998) emphasized that the first step for accident
prevention was the understanding of risk factors contributing to accidents, analyzing
the distribution of four major fatalities including falls, struck-by, electrical shock and
caught in/or between accidents and their risk sources. Choudhry and Fang (2008)
investigated why construction workers engaged in unsafe behavior in the construction
industry and identified various reasons for unsafe worker behavior through a series of
industry interviews. The determined factors included ignorance and lack of safety
knowledge, failure to follow safety procedures, and attitudes towards safety that
included not wearing personal protective equipment (PPE), unsafe work conditions, a
lack of skill or safety training, and workers’ failure to identify unsafe conditions
during work. Garrett and Teizer (2009) similarly investigated organizational and
supervisory human factors and workers’ mental and physical conditions which
eventually led to human errors on a job site, proposing a framework of human error
awareness training and discussing the potential for site safety control. Suraji et al.
(2001) highlighted the complex interaction of factors in accident causation and
proposed an empirical accident causation model. They identified different groups of
proximal factors and event characteristics in accident causation, including
inappropriate construction planning, inappropriate construction operation or control,
inappropriate site conditions, inappropriate ground conditions, an unacceptably noisy
or crowded environment, and inappropriate operative action. The importance of PPE
and safety devices, proper site inspections, a safe working environment, safety culture, safety training, and supervision have also been emphasized by many
researchers including Sawacha et al. (1999), Tam et al. (2004), Haslam et al. (2005),
Aksorn and Hadikusumo (2008), Cheng et al. (2010), Ismail et al. (2012), and Leung
et al. (2012). Table 1 grouped existing risk assessment studies and accident risk
factors into three categories: unsafe workers’ behaviors, unsafe working conditions,
and exposure to hazardous injury sources.
< Insert Table 1 here >
Despite these achievements, there is a distinct lack of studies that investigate
specific inter-relationships among different risk elements including unsafe acts,
mechanical hazards, and environmental conditions that were identified as key
accident causes by Heinrich (Heinrich, 1936); few studies explored the combination
effects among different risk factors on accident generation and injury severity.
Firenze’s systems theory (1978) responds well to this need. Firenze considered
accident causation as a system that is a group of interacting and interrelated risk
components and emphasized a harmony between human, machine, and environment
for accident prevention. Instead of considering the environment as being full of risks
and the people as being error prone, he assumed the chance of an accident is low
under normal, harmonized circumstances. Changes in interrelationships can increase
or reduce the likelihood of an accident (Goetsch, 2011). Systems theory has been
applied to risk analyses of a range of engineering processes. McIntyre (2002)
developed system-based techniques for aircraft systems’ safety risk assessments and management and Leveson (2003) provided a theoretical framework for safer
engineering process design and efficient risk identification using systems theory.
The study presented in this paper incorporates systems theory into Heinrich
(1936)’s model to better understand interrelationships between construction safety
risks and to break the chain of accident causation (Figure 1). To achieve the research
aim, the study reviewed 9,358 accident cases which occurred in the U.S. construction
industry between 2002 and 2011. The large case number supported practical,
empirical, and statistical analyses. Specific research objectives and their contributions
are discussed below:
1) To understand the relationships between accidents and injury elements
(e.g., injury types, part of body injured, degree of injury) and the nature of
construction injuries by different accident types (#1 in Figure 1). This
would motivate construction workers to improve accident prevention,
support post-accident rehabilitation and management, and assist safety
managers to better understand the severity of each accident type and
prioritize managerial effort for accident prevention.
2) To understand the relationships between accidents and human (e.g.,
worker behavior), mechanical (e.g., injury sources such as tools or
equipment), and physical (e.g., environmental conditions) risk factors (#2
in Figure 1) and identify key relationships among risk factors (#3 in
Figure 1). Since every accident has its root causes, it is believed that an
accident can be prevented by eliminating these causes. Thus, the
likelihood of an accident may be reduced by identifying combinations of key causes of each accident type and keeping the balance among them. It
would also help safety managers to develop a strategic risk mitigation plan
and prevent accident causation.
< Insert Figure 1 here >
The accident examples investigated in this study included accidents in the
building and infrastructure construction sectors. As shown in Figure 1, the scope of
this study was limited to accident risk relationships and their impact analyses during
accident and injury causation. Heinrich (1936) pointed out that injuries are caused by
preceding factors, and the action of these preceding factors can be negated by
understanding and removing the unsafe behaviors and conditions. Although it is ideal
to eliminate such unsafe acts and conditions in advance by controlling social,
organizational, and workers’ psychological risk factors (first two dominos), the
unsafe acts and conditions tend to still exist on construction sites due to the dynamic,
unpredictable, and complex nature of construction projects and operations. Thus, this
research scope widens a gap between dominos and breaks the chain of events by
managing the relationships among risk factors and making strategic risk management
and injury prevention plans.
This paper is organized into four sections. After this introduction, Section 2
describes the U.S. Occupational Safety and Health Administration’s (OSHA’s)
accident investigation reports and data analysis processes. Section 3 then discusses
research findings on perceptions of construction injuries and the identification of key
risk relationships and Section 4 concludes the article with contributions and
recommendations for future research.
2. Analysis of OSHA Accident Reports
2.1 Data description
This study reviewed 9,358 accidents which occurred in the U.S. construction
industry over the past 10 years, between 2002 and 2011. The accident data was
obtained from OSHA. OSHA reports seven data categories during accident
investigation: (1) environmental risk factors, (2) human risk factors, (3) source of
injury, (4) accident type, (5) injury type, (6) part of body injured, and (7) degree of
injury. The dataset used in this study comprised 3,124 fatalities (33.4%), 5,210
hospitalized injuries (55.7%), and 1,024 non-hospitalized injuries (10.9%), which is
the degree of injury. The accidents included: 4,110 falls from an elevation or at the
same level (43.9%); 2,409 struck by/or against (25.7%); 934 caught in/or between
(10.0%); 567 electrical shocks (6.1%); 247 inhalation, ingestion or absorption (2.6%);
179 cardiothoracic, vascular or respiratory failure (1.9%); and 912 ‘other’ (9.7%)
which encompasses a range of miscellaneous accident types. The original dataset
included several low-frequency accident types having 100 or less observations but
they were combined with the ‘other’ category for more reliable statistical analysis.
Table 2 summarizes specific data elements of other data categories.
< Insert Table 2 here >
In the reviewed OSHA accident reports, the victims included construction
inspectors, architects, surveyors, supervisors, masons, tile setters, carpet installers,
carpenters, drywall installers, electricians, painters, plasterers, plumbers, concrete
finishers, glaziers, insulation workers, roofers, duct installers, structural metal
workers, earth drillers, construction trade workers, welders and cutters, crane and
tower crane operators, heavy machinery operators, and other general construction
2.2 Data analysis
Figure 2 illustrates the data analysis methodology used to achieve the research
objectives. Before conducting detailed analysis for each objective, the authors
verified relationships identified by Heinrich (1936) and Firenze (1978) with OSHA’s
accident data to understand their applicability to recent accident causation and build a
foundation for further analysis. For instance, the analysis to understand the nature of
injury by different accident types can be more meaningful once their correlation is
identified. The authors employed the Chi-square analysis developed by Karl Pearson
(1900) and Fisher’s exact test (Fisher, 1954; Agresti, 1992) to explain three
relationships between (1) accidents and injuries, (2) risk factors and accidents, and (3)
different risk factors. For the accident and injury relationship analysis, three detailed
relationships were also investigated: accidents and injury types, accidents and parts of
body injured, and accidents and degree of injury. The risk and accident relationship
analysis explored the following relationships: (1) accidents and worker behaviors, (2)
accidents and environmental conditions, and (3) accidents and sources of injury. The
relationships among those three risk factors were then investigated to verify Firenze’s
systems theory (1978). The conditional probability, p-value, was calculated for each
relationship through the use of SPSS statistical analysis software and a p-value of
0.01 (1%) or less was chosen as an acceptable significance level for more reliable
analysis considering the large number of sample sizes obtained from the accident
data. When the p-value was less than the acceptable level, the null hypothesis “there
is no relationship between two variables being examined” was rejected, which means
that there was a significant correlation between the two variables. Detailed
description of the Chi-square analysis and Fisher’s exact test can be found in Pearson
(1900), Fisher (1954) and Agresti (1992).
< Insert Figure 2 here >
Once the correlations between accidents and injuries were statistically
confirmed, the authors first investigated the nature of injury by different accident
types explaining what types of injury and parts of the body were associated with each
accident type and what their severity was. The authors then identified significant
injury elements including types, parts, and severity of accidents by analyzing their
frequency. An injury element having higher frequency was determined to be more
significantly related to the accident. For instance, fracture (58%) was a major type of
injury due to falls from an elevation, and head (25%) and back (9%) were significant
parts of body injured. Hospitalized injuries (64%) dominated non-hospitalized
injuries (8%) for the falling accidents. For the second research objective, the
statistical analysis first investigated the risk and accident relationship as well as the
triangular systematic relationship among three risk factors. Further analyses were
performed on top of the correlations found in order to identify key risk factors
contributing to each accident type and significant risk combinations among risk
factors causing the accident. The frequency analysis prioritized risk factors and their
relationships. For example, a working surface condition (an environmental
condition), misjudgment (worker behavior) and a ladder (an injury source) were
determined as one of the key relationships for falls from an elevation, explaining 60
accidents, which accounted for 5% of the total falling accidents. Such relationships
identified were then summarized by a risk and accident analysis diagram.
3. Analysis Results and Discussion
3.1 Perception of construction injuries
The authors first determined correlations between accident types and injury
elements. As shown in Table 3, the p-values between (1) accidents and injury types,
(2) accidents and parts of body injured, and (3) accidents and injury severity were
less than 1%, which explained significant correlations between the investigated
variables. The results verified Heinrich (1936)’s accident and injury relationship with
recent accident data and indicated that different accident types may show different
impacts on injury severity, types, and parts, and could result in different injury
characteristics. The authors then performed frequency analysis to seek detailed
< Insert Table 3 here >
Table 4 summarizes observation frequency of: each injury severity, either
fatality, hospitalized or non-hospitalized (Table 4(a)); each injury type from
amputation to cancer (Table 4(b)); and each part of body injured such as abdomen
and reproductive system (Table 4(c)), against different accident types. The analysis
showed that the fatality rate for electrical shock accidents (65%) and respiratory
failure (96%) was higher than the rate for other accident types due to high voltage
and toxic gases leading to death. About 30% of fatality rates were identified as
resulting from most of the other accident types and their likelihood of having
hospitalized injuries was much higher than the likelihood of having non-hospitalized
injuries. The low frequency of non-hospitalized injuries indicates that most
construction accidents are severe and require lost working days due to the injury. This
is critical considering both the direct and indirect costs of injury compensation. Falls
from an elevation (42%), struck-by (23%), and caught in/or between (10%) accidents
were the top three accident types that accounted for 75% of the total workplace
injuries in the construction industry.
< Insert Table 4 here >
The analysis also considered common injury types associated with each
accident type. Based on the observed frequency, the authors identified key injury
types for each accident type if their frequency accounted for more than 5% of the
total accidents. Falls from an elevation resulted in 330 bruise/contusion/abrasion
(8%), 415 concussion (11%), and 2,275 fracture (58%) injuries among the total of
3,944 falls from an elevation. The injured body parts primarily included back (9%),
body system (9%), foot and ankle (7%), head (25%), legs (7%) and multiple body
parts (18%). Head injuries are highly related to concussions and other body parts are
linked with fractures and bruise/contusion/abrasions. Falls at the same level
determined similar injury types including 12 bruise/contusion/abrasions (7%), 9
concussions (5%), 72 fractures (43%), 9 cut/lacerations (5%), and 17 burn/scalds by
heat (10%) among the total of 166 falls at the same level. The parts of injured body
comprised arm (5%), body system (6%), foot and ankle (8%), hands (9%), head
(15%), hip (5%), and legs (13%). Only falls from an elevation, not falls at the same
level, resulted in multiple body parts injured indicating that falls from an elevation
could generate more severe injuries in general, leading to more fatalities.
Interestingly, falls at the same level caused 17 burn/scald injuries by heat because, for
instance, workers carrying a bucket of hot water or hot materials like asphalt splashed
them onto their hands when they lost balance and fell. That may be why falls at the
same level included hands as major parts of body injured. Both accident types
showed a high frequency of critical head injuries.
Struck-by, caught in/or between, and struck-against accidents resulted in
similar injury types on similar parts of the body. Struck-by/or against accidents
generally caused bruise/contusion/abrasion (8-10%), concussion (5%), and fracture
(23-31%) injuries since workers can be hit by or fall against materials or surrounding
objects. Caught in/or between accidents also caused 62 bruise/contusion/abrasion
(7%) and 195 fracture (21%) injuries. The injured body parts comprised body system
(9-10%), head (6-16%), and multiple body parts (8-15%) according to these injury
types. In contrast to falling accidents, these accidents included machinery-related
injuries such as amputation, asphyxia, puncture, and cut/laceration since they could
commonly occur during tool, equipment, or construction machinery operation. That
may be why fingers, hands, and chest injuries made up a high portion of the total
injuries. One interesting observation was that 37 electrical shocks (15%) were caused
by struck-against accidents. This was due to OSHA classifying some of electrical
shock accidents as struck-against when workers were hit against energized materials
or equipment parts during their work.
Electrical shock accidents resulted in 90% of the electric shock injuries,
damaging body parts such as arm (7%) or hands (22%) that contacted a powerline or
an energized material. High voltage caused critical injuries to body systems (35%) or
multiple body parts (11%) resulting in a high likelihood of fatality. Most inhalation
accidents were related to asphyxia (40%) and poisoning (23%) causing damage to
body systems (29%), blood (20%) or lungs (35%) since they were heavily related to
toxic gases. Lastly, respiratory failure resulted in asphyxia (10%), electric shock
(17%) or heat exhaustion (8%) on body systems (32%) or chest (11%). A confined
space was one of the major sources of asphyxia and some electrical contacts (e.g. to
the chest) were able to cause respiratory failure due to heart attack.
These results can be used to support post-accident rehabilitation and
management by providing information about which part of the body can generally be
injured due to accidents and assist safety managers to understand the type of injury
related to the accident, the severity of each accident type and prioritize managerial
effort for accident prevention. The injury information can also be used to motivate
construction workers for safety enhancement purposes.
3.2 Identification of key risk factors associated with accidents
Once the nature of construction injuries was examined by different accident
types, the authors determined correlations between accident types and risk factors. As
shown in Table 5, the p-values between (1) accidents and environmental conditions,
(2) accidents and worker behaviors, and (3) accidents and sources of injury were less
than 1%, which identified significant correlations between them. The results showed
that Heinrich (1936)’s risk and accident relationship was applicable to OSHA’s
recent accident data between 2002 and 2011, and different combinations of risk
factors on a construction site may cause different types of accidents.
< Insert Table 5 here >
The authors then performed frequency analysis to identify key risk factors
associated with each accident type. As shown in Table 6, the frequency of
environmental risks, human risks, and sources of injury occurrence were observed by
different accident types. Again, based on the observed frequency, the authors
identified key risk factors if their frequency accounted for more than 5% of the total
accidents. Approximately 50% of falls from an elevation occurred due to poor
working surfaces or layout conditions since they could allow workers to lose their
balance, slip, and fall while working. Overhead moving or falling object action and
materials handling equipment or method resulted in about 11% of falls from an
elevation; for instance, by pushing workers at the edge of a working platform.
Misjudgment of hazardous situations such as surrounding moving objects or
structures (30%), safety devices removed or inoperative (12%), inappropriate
equipment operation (8%), malfunction in securing or warning operation (6%),
inappropriate working position (6%), and lack of PPE (6%) were the major human
errors that resulted from falls from an elevation. Working surfaces (29%),
surrounding buildings or structures (18%), ladders (17%) and bodily motion during
work (13%) were the major sources of injury occurrence.
Similarly, 45% of falls at the same level occurred due to poor working surface
or layout conditions and 7% resulted from materials handling equipment. This was
related to the fact that 5% of falls at the same level were caused by inappropriate
materials handling procedure and another 5% occurred as a result of insufficient
housekeeping programs. Worker misjudgment caused 30% of same level falling
accidents, which was the highest rate of worker-related risk factors. The major
sources of these accident injuries included working surfaces (31%), bodily motion
during work (16%), and surrounding buildings and structures (5%).
< Insert Table 6 here >
Approximately 52% of struck-by accidents were caused by flying object
action, overhead moving or falling object action and materials handling equipment or
method. Workers could be exposed to being hit by objects or equipment during their
work. Another 8% were related to working surfaces or layout conditions. Surface
failure resulted in workers being struck by surrounding structures or buildings. The
major human errors included misjudgment of hazardous situation (32%), malfunction
in securing or warning operation (9%), inappropriate materials handling procedure
(8%), inappropriate working position (7%), and safety devices removed or
inoperative (6%). Workers were mainly struck by highway or industrial motor
vehicles (16%), buildings or structures (13%), powered hand tools (13%), materials
handling equipment (11%), construction machinery (5%), hoisting apparatus (6%),
and metal products (5%).
Caught in/or between and struck-against accidents were more related to
machinery operation. During repeated operation of construction machinery, such as
electrical saws or cutters, workers tended to be exposed to the risks of having caught
in/or between or struck-against accidents as a result of pinch, catch, shear, or squeeze
point actions. About 60% of caught in/or between accidents were the result of these
actions and 20% of struck-against accidents occurred due to catch or shear point
actions. Similarly to struck-by accidents, materials handling equipment or methods
were responsible for 17% of struck-against accidents and poor surface or layout
conditions resulted in 24% of the accidents. Another 6% of struck-against accidents
were caused by overhead moving or falling object action. These three environmental
risk factors were also major sources of caught in/or between accidents generating 9%,
6%, and 9% of them respectively. Misjudgment, malfunction in securing or warning
operation, inappropriate equipment operation, safety devices removed or inoperative,
inappropriate working position, and inappropriate materials handling procedure were
the major human-related risks attributing to both caught in/or between and struckagainst
accidents. Machine (22%), materials handling equipment (13%),
dirt/sand/stone (11%), industrial motor vehicle (9%), powered hand tool (7%),
hoisting apparatus (6%) and buildings/structures (5%) were the common sources of
caught in/or between injuries. They were generally operation or equipment
inspection-related injury sources. Struck-against accidents were the result of similar
sources, with the exception of electrical apparatus or wiring which caused 17% of the
accidents. Again, that was because OSHA classified some electrical shock accidents
as struck-against accidents when workers were hit against energized materials or
equipment parts during their work.
Characteristics of electrical shocks were more straightforward: 86% of
electrical shocks were the result of electrical apparatus or wiring (source of injury
occurrence); 20% occurred due to poor working surface or layout conditions since
they could allow workers to lose their balance and touch an energized material,
equipment or a powerline; and another 11% occurred due to contact with energized
materials handling equipment. Misjudgment of hazardous situations (41%), lockout/
tag-out procedure malfunction (12%), inappropriate working position (7%) and
lack of PPE (7%), were the major human-related risk factors.
Eighty one percent of inhalation accidents occurred due to gases, vapor, mist,
fume, smoke, or dust and another 7% were caused by exposure to chemical action or
reaction. The common risk factors of inhalation included misjudgment (32%), lack of
engineering control (18%), inappropriate equipment operation (8%), lack of
respiratory protection (8%), and inappropriate materials handling procedure (6%).
Inappropriate operation caused equipment failure or structural damage, such as
pipeline cuts, resulting in fire or gas exposure leading to inhalation accidents. The
major sources of injury were gases (36%), chemical liquid or vapors (35%), fumes
(6%), and fire/smoke (5%).
Lastly, there was no dominant environmental factor causing respiratory failure
since this accident primarily occurred as a result of a heart attack or a worker’s other
physical health problems and thus it was difficult to determine the direct source.
Temperature above or below tolerance level had the highest frequency rate of 7%
because electrical shocks sometimes led to a heart attack or respiratory problems. The
common human errors related to this accident included misjudgment (10%) and
malfunction in securing or warning operation (6%). There were two main sources of
injury: electrical apparatus and wiring (17%); and heat (8%), for example causing
By combining the results of the frequency analyses discussed above, the
authors identified 11 key environmental conditions (pinch point action, catch
point/puncture action, shear point action, squeeze point action, flying object action,
overhead moving and/or falling object action, gas/vapor/mist/fume/smoke/dust
condition, materials handling equipment/method, chemical action/reaction exposure,
temperature above or below tolerance level, and working surface/facility layout
condition), 11 key worker behaviors (misjudgment of hazardous situation,
malfunction of procedure for securing operation or warning of hazardous situation,
equipment in use not appropriate for operation or process, safety devices removed or
inoperative, operational position not appropriate for task, procedure for handling
materials not appropriate for task, malfunction of procedure for lock-out or tag-out,
insufficient or lack of housekeeping program, insufficient or lack of engineering
controls, insufficient or lack of respiratory protection, and insufficient or lack of
protection work clothing and equipment), and 18 significant sources of injury
occurrence (bodily motion, buildings/structures, chemical liquid/vapors,
dirt/sand/stone, electrical apparatus/wiring, fire/smoke, gases, powered hand tool,
heat, hoisting apparatus, ladder, machine, materials handling equipment, metal
products, highway motor vehicle, industrial motor vehicle, working surface, and
fume) that were highly related to construction accidents.
3.3 Identification of key risk relationships contributing to accidents
Next, the authors investigated the correlations among three risk factors
(environmental condition, worker behavior, and source of injury occurrence) to test
the applicability of Firenze (1978)’s systems theory. As shown in Table 7, all of the
p-values between (1) environmental conditions and injury sources, (2) injury sources
and worker behaviors, and (3) worker behaviors and environmental conditions were
less than 1%, which indicated significant correlations among different risk factors;
this is the concept of systems theory. In a normal working condition, when human,
mechanical, and physical conditions are well balanced, the chance of accidents
occurring becomes low. However, if one side of the triangle loses the balance—for
instance, with poor worker behavior such as inappropriate use of PPE—the likelihood
of accidents will increase.
< Insert Table 7 here >
The authors then investigated detailed risk relationships among three risk
factors which contributed to accident causation by using previously identified key
risk factors. From the 9,358 accident reports, the authors explored all the possible
relationships of three risk factors (e.g., ‘working surface’ as an environmental
condition, ‘lack of PPE’ as worker behavior, and ‘buildings or structures’ as a source
of injury occurrence) and counted the frequency of each combination associated with
each accident type. The authors identified key risk combinations if their frequency
accounted for more than 1% of the total accidents in order to explain as many
possible accident cases as practical. Table 8 summarizes the identified key
combinations by different accident types. An example of a key combination and its
contribution to accident occurrence was reviewed from the original accident reports
to confirm the identified relationship.
< Insert Table 8 here >
Falling from an elevation occurred as a result of 10 key combinations among
three risk factors. The major environmental conditions were poor working surface or
layout conditions, while misjudgment, safety devices removed or inoperative, lack of
PPE, malfunction in securing or warning operation, and inappropriate equipment
operation were the major human errors. Sources of injury occurrence included
working surface, buildings or structures, bodily motion, and ladder.
There were four key relationships attributing to struck-by accidents.
Misjudgment was the main human error, while overhead moving or falling object
action, materials handling equipment, and flying object action were the major
environmental conditions. The sources of injury included buildings or structure,
materials handling equipment, and powered hand tool.
Eight key relationships were determined for caught in/or between accidents,
and most of the environmental conditions were related to machinery actions.
Misjudgment was the major human error, and the common injury sources included
machines, materials handling equipment, dirt/sand/stone, and industrial motor
Electrical shocks were caused by seven key risk combinations, and their
injury sources were primarily electrical apparatus or wiring. Working surface
condition, materials handling equipment or method, and overhead moving or falling
object action were the main environmental risk factors associated with this accident
type, while misjudgment, inappropriate task position, lockout/tagout procedure
malfunction, lack of PPE, and safety devices removed or inoperative were the
common unsafe acts of workers.
Analysis identified 12 key relationships attributing to struck-against accidents.
Materials handling equipment or method, working surface or layout condition, and
shear or catch point actions were the primary environmental factors, and
misjudgment, safety devices removed or inoperative, and lack of PPE were the major
human errors. Struck-against accidents occurred as a result of various sources such as
powered hand tools and buildings/structures.
Inhalation was caused by 12 key risk relationships. Most of the significant
environmental conditions and injury sources were gases and chemicals. Misjudgment,
lack of engineering control, inappropriate equipment operation or materials handling
procedure, and lockout/tagout procedure malfunction were the major human errors.
Respiratory failure was associated with three risk relationships. Similarly to
inhalation, the common environmental conditions were gases, temperature above or
below tolerance level, and chemical exposure. The injury sources included gases and
heat, and the major human errors were misjudgment and malfunction in
Lastly, six relationships were identified for falls at the same level. Working
surface condition, pinch point action, and overhead moving or falling object action
were the main environmental risks, and misjudgment, inappropriate materials
handling, and electrical apparatus or wiring were the common human errors. Bodily
motion, working surface, buildings/structures, and chemical liquid or vapor were the
major sources of fall occurrence at the same level.
Table 9 provides examples of accident information provided in the original
accident reports along with the corresponding risk combinations.
< Insert Table 9 here >
The identified key risk relationships summarized in Table 8 will assist safety
managers to understand possible risk combinations that contribute to each accident
type and enable them to balance those risk factors and develop a strategic risk
mitigation plan to prevent accident causation and maintain site safety. For instance, if
safety managers want to reduce falling from an elevation during roof construction
they can enforce securing and warning operations to reduce workers’ misjudgment,
train operators to prevent them from inappropriate equipment/tool operation, inspect
safety devices if they are removed or inoperative, and provide proper PPE for injury
protection. These efforts will reduce the likelihood of human errors that can lead to
construction accidents. They can be also linked with relevant environmental risks
such as working surface or layout condition and materials handling equipment or
method to prevent workers from being negatively affected by unexpected working
conditions leading to falling accidents. Conversely, if safety managers identify risky
conditions and the defects of injury sources such as equipment, machinery, or
structure during safety inspections, the findings of this study will help them
understand which type of accident can be associated with the given risks and what
impacts (e.g., injury severity) they would have as a result of the accident.
4. Conclusions and Recommendations
This study analyzed 9,358 accidents that occurred in the U.S. construction
industry and incorporated systems theory into Heinrich (1936)’s domino theory to
better understand interrelationships between construction risks and accident
causation. Fundamental correlations between accidents and injuries and those
between risks and accidents were tested by the Chi-square analysis and Fisher’s exact
test, which verified the applicability of Heinrich’s theory to the given data set and
reliability of the accident data reviewed. Correlations among different risk factors
including environmental condition, worker behavior, and injury source were also
statistically identified, which satisfied Firenze (1978)’s systems theory. The authors
then discussed the nature of injury including injury types, parts of body injured, and
injury severity by different accident types, identified key risk factors associated with
each accident, and finally determined key risk combinations contributing to the
accident. The outcomes of the study will assist safety managers to better understand
risk factors related to different accidents and control specific risk factors (e.g., human
errors) by eliminating the associated risk factors (e.g., environmental conditions or
injury sources) to break the chain of accident causation. Safety managers can also
prioritize risk factors according to the likelihood of accident occurrence and injury
characteristics and pay more attention to controlling significant risks to achieve a
safer working environment. Additionally, the injury-related information can support
post-accident rehabilitation and management by providing information about which
part of the body can be generally injured due to the accident and assist safety
managers to understand injury types and injury severity related to the accident.
The scope of this study was limited to accident risk relationships and their
impact analyses during accident and injury causation. In future research they can be
linked with social, organizational, and workers’ psychological safety issues for more
thorough risk management and accident prevention since safety management is a
more integrated process throughout the construction life cycle. Also, the study
outcomes will benefit strategic safety information retrieval for safety inspection by
explaining which information is important to be considered and by providing
accident- or condition-specific step-by-step inspection guidelines. Risk assessment
and safety performance measurement techniques can be incorporated to evaluate the
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