Occupational safety risk analysis in construction sites based on fuzzy analytic hierarchy process: A case study in a large construction project

Abstract

BACKGROUND:

Construction projects are one of the most critical occupational sectors that experienced many challenges in occupational accidents and safety performance.

OBJECTIVE:

This study was designed to assess safety risk in construction projects based on fuzzy analytic hierarchy process.

METHODS:

This study was conducted with 12 construction and occupational safety experts in one of the largest construction projects in Tehran-Iran in 2020. The process of this study included (1) risk identification, (2) measurement of risk parameters and sub-parameters, and (3) risk assessment based on a fuzzy analytic hierarchy process. Risk-forming parameters in this study included the probability and severity of the event. The probability of occurrence was estimated based on four sub-parameters of technical inspection, accident experience, detection probability, and human reliability. Sub-parameters of severity included human injury, cost imposition, tarnishing the organization’s esteem, and impact on project timing and work stoppage.

RESULTS:

Twenty-eight identified hazards were examined in the studied construction project, including falling from a height (9-hazard), falling objects (2-hazard), electric shock (6-hazard), falling crane or load (6-hazard), elevator crashes (2-hazard), and soil fall (3-hazard). Safety risk assessment revealed that 27 risk sources were at the tolerable level and one risk source was unacceptable.

CONCLUSION:

This study demonstrated that the risk levels in the studied construction project were tolerable and unacceptable. The obtained model in this study demonstrated that using parameters that determine the probability and severity of risk according to the nature of the working environments can be a practical step in risk evaluating and implementing control measures.

Keywords

Construction project safety human injury risk assessment FAHP

1 Introduction

The construction industry is one of the largest industries with the highest number of employees in most countries, and the level of the safety risk, or in other words, the probability of occurrence and severity of various harmful events in this industry, is high [1]. The available statistics indicates that this industry has the most unfavorable occupational accident rate among all industries [2]. In this industry, various occupational groups (including workers, engineers, supervisors, and managers) are directly and indirectly exposed to the risk of underlying factors related to construction activities [3, 4].

Construction projects experienced many challenges in occupational accidents and safety performance [5]. It has been found that 25–50% of all catastrophic accidents in industrialized countries are related to construction activities [6]. Accidents and damage to construction projects in the United States are 50% higher than in other industries [7 –10]. In China, the construction industry’s accidents and deaths have been increasing rapidly in recent years [11]. Safety conditions in construction sites are much worse in developing countries. Reports of occupational accidents and deaths in the Middle East are reported at 18.6 per 100,000 workers, compared with 4.2 for developed countries [12]. In Iran, 37% of occupational accidents occur in construction projects, while this industry’s employment rate includes 10% of the country’s labor force [13]. In Iran, construction accidents account for almost half of occupational accidents. Meanwhile, in recent years, the number of injuries and casualties due to occupational accidents has increased, so that in 2016 a growth of 10%, and in 2017 a growth of 1.9% of casualties due to work accidents were recorded [14].

One of the most important ways to reduce incidents and accidents in construction projects is to use risk management and assessment appropriate to the type of working conditions. For this purpose, all existing potential hazards are first identified and evaluated, and proper control and corrective measures are taken following the obtained results [6 , 16]. Despite many efforts in the field of safety assessment in construction, most of the existing methods have specific complexities and goals. They have not met the criteria of a comprehensive strategy with all the features of a reliable safety risk assessment system in construction environments. Safety risk assessments to improve safety performance in these projects should be practical and easy-to-use.

Besides, due to the nature of risk assessment and the type of events that occur in construction projects, there is no clear boundary and range to determine the probability and outcome indicators of these events, so using a method that can specifically cover these risk areas is very appropriat, and it will be helpful. Another critical issue in the types of risk assessment is the lack of attention to the parameters for determining the index and probability rate. They are essential sources through which the index and probability rate can be estimated considering the types of information sources and available data for determining and evaluating the relative probability rate, such as technical and safety inspection data, past accidents records, and the reliability and performance of workforce can be of great importance. Also, paying attention to the types of consequences and damages in the construction industry, including human damages, damage to project assets, damage to the organization’s credibility and reputation, and prolongation of construction projects, can help estimate the severity rate more accurately.

Therefore, due to the lack of a relatively comprehensive technique that can examine the most critical components affecting the probability and severity of accidents in the construction industry as one of the most vulnerable and high-risk industries in the world, and also a need for a comprehensive, practical, specific, and at the same time accurate and easy-to-use technique to increase the level of safety in construction projects, this study was designed and conducted to assess safety risk in construction projects based on fuzzy analytic hierarchy process (FAHP).

2 Methods

2.1 Study design

This cross-sectional and practical study was conducted in 2020 using a semi-quantitative safety risk assessment technique in one of the largest construction projects in Tehran-Iran based on FAHP. This semi-quantitative safety risk assessment technique was created and validated during the study of Mahdinia et al. This method has been developed according to the nature of risks in the construction industry [17].

Risk assessment in this study includes three steps:

Identification of safety hazards in the construction project.

Measurement and numerical estimation of risk parameters and sub-parameters based on semi-quantitative safety risk assessment technique.

Safety risk assessment of each identified hazard with the basis of FAHP.

In this study, 12 construction experts, including managers (3 people), supervisors (2 people), safety officials (5 people), and experienced workers (2 people), participated. These subjects were selected by simple random sampling among individuals working on large construction projects in Iran.

2.2 Hazard identification (HAZID)

Identifying safety hazards in the studied construction project is based on risk identification checklists related to construction projects, description and analysis of various activities in this project, review of various studies on hazard identification, and safety risk assessment in construction projects.

2.3 Measurement of risk parameters and sub-parameters

Numerical measurement and estimation of risk parameters and sub-parameters based on semi-quantitative safety risk assessment techniques were performed. Risk assessment in this study was based on a two-dimensional matrix including probability and severity parameters. The probability of the event’s occurrence was estimated based on four sub-parameters of technical inspection, accident experience, the likelihood of detection, and human reliability (Table 1). The event’s severity was estimated using the sub-parameters of human harm, cost imposition, destruction of the organization’s esteems, and impact on project time and work stoppage (Table 2).

Table 1
Guide to determining the probability of occurrence [17]

Score Technical inspection Incident experience Detection probability Human reliability (HR)

1 Weekly Incident data has been available in similar projects and root analysis has been performed Certainly with the existing controls, the danger is detected and revealed Regarding this risk, human reliability is assessed, behavior based safety (BBS) program implemented, training program implemented and trainings monitored

2 Monthly Accident data is only available from the employer records of the project and root analysis has been performed It is probable (>50%) that the risk can be detected with existing controls Regarding this risk, the training program is implemented and the trainings are monitored

3 Every three months Incident data is available from the project employer records. Only descriptive analysis has been done It is probable (<50%) that the risk can be detected with existing controls Regarding this risk, a training program is implemented

4 Every six months Incident data is available from the project employer records. No analysis has been done It is unlikely (<10%) that risk can be detected and detected with existing controls Regarding this risk, only the legally required training has been implemented incompletely and compulsorily

5 Up to once during the life of the project No incident data available There is no control or if there is, it is not able to detect the danger Regarding this risk, no action is taken to assess human reliability, implement behavior based safety (BBS), train and monitoring

Score	Technical inspection	Incident experience	Detection probability	Human reliability (HR)
1	Weekly	Incident data has been available in similar projects and root analysis has been performed	Certainly with the existing controls, the danger is detected and revealed	Regarding this risk, human reliability is assessed, behavior based safety (BBS) program implemented, training program implemented and trainings monitored
2	Monthly	Accident data is only available from the employer records of the project and root analysis has been performed	It is probable (>50%) that the risk can be detected with existing controls	Regarding this risk, the training program is implemented and the trainings are monitored
3	Every three months	Incident data is available from the project employer records. Only descriptive analysis has been done	It is probable (<50%) that the risk can be detected with existing controls	Regarding this risk, a training program is implemented
4	Every six months	Incident data is available from the project employer records. No analysis has been done	It is unlikely (<10%) that risk can be detected and detected with existing controls	Regarding this risk, only the legally required training has been implemented incompletely and compulsorily
5	Up to once during the life of the project	No incident data available	There is no control or if there is, it is not able to detect the danger	Regarding this risk, no action is taken to assess human reliability, implement behavior based safety (BBS), train and monitoring

Table 2

Guide to determining the severity of occurrence [17]

Score	Human injury	Financial loss	Reputation damage	Operational interruption
1	Minor injuries and trauma as needed for first aid treatment	Less than 2500 $	Imperceptible reflection of news	Project suspension for less than 2 hours
2	Moderate injuries and trauma leading to short-term hospitalization (up to three days)	2500–5000 $	Reflection of news among stakeholders	Project suspension for up to 1 day
3	Severe injuries and trauma leading to long-term hospitalization (more than three days)	5000–10000 $	Reflection of news among stakeholders and social media	Project suspension for 1 day to 1 week
4	Injuries leading to amputation and disability	10000–25000 $	Reflection of news among stakeholders and social media and widely circulated newspapers	Project suspension for 1 week to 1 month
5	Death of one or more people	More than 25000 $	News coverage among stakeholders, social media, widely circulated newspapers, national and international	Project suspension for more than 1 month

2.3.1 Probability of occurrence

The probability component in the concept of risk is the probability of an incident occurring within a certain period, which in this study was determined using the following parameters.

2.3.1.1. Detection probability: The means or method by which a failure is detected, isolated by operator and maintainer, and the time it may take. This is important for maintainability control and is essential for multiple failure scenarios. This may involve dormant failure modes (e.g., No direct system effect, while a redundant system/item automatically takes over or when the failure only is problematic during a specific mission or system states) or latent failures (e.g., deterioration failure mechanisms, like a metal growing crack, but not a critical length). It should be clear how an operator can discover the failure mode or cause under regular system operation or if the maintenance crew can find it by some diagnostic action or automatically built-in system test. A dormancy and latency period may be entered [17].

The detection probability parameter is one of the important parameters in determining the risk number of various hazards, which is also present in methods such as FMEA (failure mode and effect analysis). Increasing the probability of discovering a source of danger reduces the likelihood of its occurrence and changing risk from potential to actual status. It can be said that the probability of discovering a risk has an inverse relationship with the likelihood of its occurrence. Therefore, the detection probability parameter is an essential concept in investigating the likelihood of an incident occurring in different occupational sectors.

2.3.1.2. Human reliability: Human reliability refers to the likelihood of successful human performance within selected timeframes and environmental requirements. It is critical to overall system reliability and is one factor that contributes to or prevents unwanted events from occurring.

As human reliability increases in a system, human error decreases and vice versa. Human error is one of the important parameters in determining the probability of accidents. Statistics show that 88% of accidents were due to human error (Human error or violations) and unsafe acts, and 10% were due to unsafe conditions [18].

2.3.1.3. Technical inspection: A technical inspection is used to verify compliance with technical specifications. The inspection may be conducted visually, or specific instrumentation may be required to determine whether equipment or installations comply with the relevant technical specifications. The special equipment or facilities determine the nature and extent of technical inspections [17].

It has been determined that as the amount of technical inspection of equipment and various processes in the work environment increases, the probability of discovering failures and errors in the system will decrease.

2.3.1.4. Accident experience: The accident experience and generally learning from accidents is one of the important parameters in determining the probability of accidents. It has been determined that people who had an accident in the workplace are less prone to accidents due to the experience they have with negative consequences. As the amount of experience of events and learning from events in the industry increases, the reoccurrence of events can decrease by implementing corrective measures.

2.3.2 Severity of occurrence

The severity component in the concept of risk is the range of losses and damages that can be caused if the source of risk becomes factual. It is clear from this concept that this parameter can be measured and determined through the following important aspects [17]: human injury, financial loss, operational interruption and reputation damage.

2.4 Risk assessment

In general, the concept of risk consists of two components: the probability of occurrence of a hazard in a certain period and the range of severity due to the occurrence of potential hazards [19]. The results of the previous studies indicated that factors such as the technical inspection, human reliability, incident learning, and hazard detection could affect and determine the incident probability, and components such as human injury, financial loss, operational interruption, and reputation damage can determine the incident severity in the construction industries [17].

Safety risk assessment was performed based a method that has been developed based on FAHP [17]. The construction project’s safety risk assessment is designed based on a two-dimensional risk matrix including probability and severity parameters and based on defined sub-parameters for each of these parameters (Fig. 1). Levels of risk decision-making based on this technique are presented in Table 3.

Fig. 1

Construction safety risk assessment algorithm [17].

Table 3

Risk leveling [17]

CSRI	Defined risk level
<1	Level 1	Acceptable risk
1–3	Level 2	Tolerable risk: Requires corrective action in the near future
3<	Level 3	Unacceptable risk: Requires immediate corrective action

The analytic hierarchy process is one of the most popular multi-criteria decision-making methods invented by Thomas L. Saati in the 1970 s [20, 21].

Fuzzy logic is a form of the multi-valued region in which the variables’ correct values may be any real number between zero and one and zero and one itself. This logic is used to apply the concept of partial correctness so that its values can be between entirely accurate and completely false [22]. This theory is a powerful tool to deal with the ambiguity and uncertainty of human judgment and evaluation in decision-making [17, 23]. In different studies, combining the AHP method with fuzzy logic has been used to rank and weight the criteria and sub-criteria. Different methods for performing FAHP have been proposed.

This study was based on the method proposed by Chang because it is easier to implement than other methods and at the same time provides accurate results [24]. Therefore, in this study, the construction safety risk index (CSRI) and event probability and severity parameters have been calculated based on Equations 1–3 and Fig. 1 [17]. Mahdinia et al. reported that the model’s consistency index was less than 0.1 in all cases and was accepted [17]. $CRI = [Probability \times 0.486] \times [Severity \times 0.514]$ (1) $Probability = \sum P_{i} {PW}_{i}$ (2) $Severity = \sum S_{i} {SW}_{i}$ (3)

CRI: Construction risk index

Probability: Incident probability

Severity: Incident severity

Pi: Numerical index of sub-parameters of incident probability (Table 1)

PWi: Normalized weight of each of sub-parameters of incident probability (Fig. 1)

Si: Numerical index of sub-parameters of incident severity (Table 2)

SWi: Normalized weight of each of sub-parameters of incident severity (Fig. 1)

3 Results

The mean age and work experience of the participants in the present study were 43.12±8.43 and 10.51±4.71 years, respectively. All participants were male. Regarding education level, 30% had a diploma, 42% had a bachelor’s degree, and 28% had a master’s degree. The average working hours per day of the subjects was 9.00±1.2 hours.

Identifying safety hazards in the studied construction project revealed 28 threats to the safety of human and economic capital in this project. Depending on the type of event, these hazards include falling from a height (9-hazard) and falling objects (2-hazard), electric shock (6-hazard), falling crane or load (6-hazard), elevator fall (2-hazard), and soil fall (3-hazard). The risk assessment results of these 28 risk sources revealed that the level of safety risk of one risk source was at the level of unacceptable risk, and 27 sources of risk were at the level of tolerable risk.

Findings of risk assessment associated with falling from a height showed that all risk sources’ risk level was tolerable (level 2). The level of safety risk related to the two sources of risk for a possible fall from a height, including failure to perform specialized training for work at height to express the work and the risks associated with this activity and failure to perform occupational medicine examinations and use of personnel with epilepsy, hypertension, cardiac, visual, and auditory problems have been calculated to a tolerable level and requiring corrective action soon (level 2) (2.270 and 2.467, respectively). Also, the safety risk of falling objects was estimated for two sources of danger, including not enclosing the surface below the workstations with a hazard bar or rigid barrier and not using a standard helmet in the workplace. The risk indexes for these two risk sources were 1.876 and 1.591, respectively (Table 4).

Table 4
Results of fall event risk assessment in the studied construction project

Risk source Probability Severity CSRI

Technical Incident Detection Human Human Financial Reputation Operational

inspection experience probability reliability (HR) injury loss damage interruption

Failure to implement vertical and horizontal lifeline system in the installation of steel structures 2 2 1 2 5 4 4 3 1.832

Failure to execute horizontal lifeline during reinforcement and formwork of concrete structure 2 2 1 2 5 4 4 3 1.832

Lack of specialized training about working at heights 3 2 2 2 5 3 4 3 2.270

Failure to observe safety principles in the implementation of scaffolding, especially the installation of base plates, compliance with the standard of vertical pipes and horizontal ledger pipes and installation of top rail and mid rail 1 1 2 2 5 4 5 3 1.762

Do not use a fall harness lanyard 1 1 2 2 5 4 4 3 1.679

Do not use appropriate personal protective equipment 1 1 2 2 5 4 4 3 1.679

Use of unsafe ladders or unsafe use of ladders 1 2 2 3 4 3 4 2 1.743

Failure to perform occupational medicine examinations and use of personnel with epilepsy, hypertension, heart problems, vision and hearing problems in work operations at height 2 2 2 3 5 4 4 3 2.467^**

Do not use the toe board on the platforms to prevent falling objects 1 2 2 2 5 3 4 2 1.591^*

Do not enclose the surface below the workstations with a hard barrier 2 2 2 2 5 3 4 2 1.876

Do not use a standard helmet 1 2 2 2 5 3 4 2 1.591^*

Risk source	Probability	Severity	CSRI
Failure to implement vertical and horizontal lifeline system in the installation of steel structures	2	2	1	2	5	4	4	3	1.832
Failure to execute horizontal lifeline during reinforcement and formwork of concrete structure	2	2	1	2	5	4	4	3	1.832
Lack of specialized training about working at heights	3	2	2	2	5	3	4	3	2.270
Failure to observe safety principles in the implementation of scaffolding, especially the installation of base plates, compliance with the standard of vertical pipes and horizontal ledger pipes and installation of top rail and mid rail	1	1	2	2	5	4	5	3	1.762
Do not use a fall harness lanyard	1	1	2	2	5	4	4	3	1.679
Do not use appropriate personal protective equipment	1	1	2	2	5	4	4	3	1.679
Use of unsafe ladders or unsafe use of ladders	1	2	2	3	4	3	4	2	1.743
Failure to perform occupational medicine examinations and use of personnel with epilepsy, hypertension, heart problems, vision and hearing problems in work operations at height	2	2	2	3	5	4	4	3	2.467^**
Do not use the toe board on the platforms to prevent falling objects	1	2	2	2	5	3	4	2	1.591^*
Do not enclose the surface below the workstations with a hard barrier	2	2	2	2	5	3	4	2	1.876
Do not use a standard helmet	1	2	2	2	5	3	4	2	1.591^*

^*Minimum value; ^**Maximum value.

The risk assessment results of the electric shock event showed that all risk sources’ risk level was tolerable (level 2) and needed corrective measures soon. The minimum risk index was related to ignoring the electrical areas adjacent to the workshop or underground facilities inside and near the workshop, with an index of 1.793 (Table 5).

Table 5

Results of electrical shock risk assessment in the studied construction projects

Risk source	Probability				Severity				CSRI
	Technical	Incident	Detection	Human	Human	Financial	Reputation	Operational
	inspection	experience	probability	reliability (HR)	injury	loss	damage	interruption
Do not use the earthing system to protect people and equipment from electric shock	2	2	3	2	5	3	5	3	2.328
Do not use RCCB fuses with earthing system	1	2	3	2	5	3	5	3	2.014
Failure to pay attention to the electrical space adjacent to the workshop or underground facilities inside and near the workshop	2	1	3	2	5	3	4	2	1.793^*
Non-observance of safety rules in cabling inside the workshop, mobile wires, electrical panels installed in the project	2	1	3	2	5	3	4	2	2.102
Working with electrical installations by people without the necessary qualifications and expertise	2	1	3	2	5	3	4	2	2.364^**
Passing equipment and machinery over power cables and damaging them	2	1	3	2	5	3	4	2	2.023

^*Minimum value; ^**Maximum value.

The risk assessment results of crane/load fall and elevator fall in the studied construction projects showed that all eight identified sources of risk for these two events were at a tolerable risk level and required corrective measures soon (level 2). The highest level of risk for the crane/load fall event was not using fully skilled operators and using an unqualified rigger to properly close the load, control equipment, and transfer the load from the origin to the relevant destination, with a safety risk index of 2.860. Among the two sources of risk identified for the elevator fall event, failure to obtain a safety certificate for workshop elevators with a safety risk index of 2.911 had a higher risk than non-service and periodic maintenance of elevators (safety risk index = 2.188) (Table 6).

Table 6

Results of crane/load fall and elevator fall event risk assessment in the studied construction projects

Risk source	Probability				Severity				CSRI
	Technical	Incident	Detection	Human	Human	Financial	Reputation	Operational
	inspection	experience	probability	reliability (HR)	injury	loss	damage	interruption
Use of tower cranes or worn-out mobile cranes without technical inspection certificate	2	2	2	2	5	5	5	4	2.403
Malfunction of weight switches, sharia, flash, rotary and etc.	2	2	4	2	5	4	5	3	2.728
Do not use fully skilled operators	3	4	2	2	5	5	5	3	2.860
Lack of service and periodic maintenance of cranes	2	3	3	2	5	3	4	2	2.188^*
Do not use loading devices with approved or daily inspection of loading devices	2	3	2	2	5	4	5	3	2.287
Use of unqualified rigger in controlling devices and transferring load from origin to relevant destination	3	4	2	2	5	5	5	3	2.860
Failure to obtain a technical inspection certificate for workshop elevators	3	2	2	3	5	4	4	4	2.911^**
Lack of periodic service and maintenance of elevators	2	2	3	2	5	3	4	2	2.188^*

^*Minimum value; ^**Maximum value.

Table 7

Results of soil and excavation wall fall event risk assessment in the studied construction projects

Risk source	Probability				Severity				CSRI
	Technical	Incident	Detection	Human	Human	Financial	Reputation	Operational
	inspection	experience	probability	reliability (HR)	injury	loss	damage	interruption
Failure to consider safety principles during excavation to strengthen the pit wall	4	2	3	3	5	4	5	3	3.522^**
Lack of safe implementation of wall reinforcement based on current methods, nailing, piling, diaphragm wall, etc.	2	2	3	3	5	4	5	3	2.858^*
Lack of regular wall monitoring to detect soil or wall subsidence and to monitor cracks around the pit and / or on the wall	2	2	3	3	5	4	5	3	2.858^*

^*Minimum value; ^**Maximum value.

The risk assessment results of the soil and excavation wall showed that non-observance of safety principles during excavation to strengthen the excavation wall with a risk index of 3.522 was at an unacceptable risk level (requires immediate corrective action). Besides, the risk of two sources is not the safe implementation of wall reinforcement based on current methods, nailing, piling, diaphragm wall, and lack of regular wall monitoring to detect soil or wall subsidence and monitor cracks in the pit that were in the tolerable risk level. The need for corrective actions soon (level 2) has been estimated (safety risk index = 2.858).

4 Discussion

Researchers have begun implementing various techniques for predicting construction safety performance, including safety risk analysis, leading indicators, precursor analysis, and safety climate. Meanwhile, it is very important to develop a comprehensive risk assessment method according to the nature of risk factors and hazards in the work environment in order to systematically implement the risk management process [25].

Various studies demonstrated that construction projects are one of the most dangerous industries due to their unique and dynamic nature [1 , 26–28]. The severity of losses and damages caused by construction projects is such that creating a suitable platform for the risk management process and reducing accidents in many developed and developing countries has become a national priority [29]. In these projects, each person is directly exposed to a high volume of risk factors affecting accidents. In addition to causing harm to human resources, the risks in these projects can affect various aspects of the industry, such as current project costs, quality of work, time planning of activities, the credibility of the organization, etc. [30]. Other studies show that the mentioned risk factors include personal, occupational, environmental (unsafe conditions), unsafe acts, and managerial-organizational factors [31, 32]. The unique features of construction projects that lead to lower levels of safety and increase the rate of accidents can be duo to continually changing conditions and specifications of the work environment, the use of various equipment and materials during tasks, lack of proper housekeeping in the workplace, the temporary employment of workers and the unsafe conditions created by being in the workplace (exposure to noise, vibration, dust, cold and heat stress, etc.) [5].

In addition to human harm, the high frequency of accidents in these industries imposes extensive financial consequences on communities [33]. Accordingly, attention to the risk management process in the form of a forward-looking (proactive) approach, especially in work environments with a high volume of risk factors, such as construction projects, has become more apparent. The risk management algorithm in different studies consists of various phases such as system description, hazard identification (HAZID), risk assessment, risk evaluation, and control measures. Among these, the use of different risk assessment methods as the heart of risk management systems and the basis for decision-making on existing risks has particular importance [34].

The results of risk assessment such as falling from a height, falling objects, electric shock, crane/load falling, elevator fall, and soil fall in the studied construction project revealed that the level of safety risk based on the fuzzy analytical hierarchical process in 27 risk source were at tolerable level and in one source was at unacceptable risk, which indicates the lack of proper and desirable safety conditions. Out of the nine identified risks for falling from a height, the level of risk threatening the safety and health of human and economic capital, seven risks were estimated as minimum. Also, the results indicated that the level of safety risk related to two sources of risk, including not performing specialized training for work at height and the associated risks with this activity and not performing occupational medicine examinations, and using personnel with epilepsy, hypertension, cardiac, visual, and auditory problems have been calculated at tolerable risk level and requiring corrective action soon. Previous research revealed that significant accidents related to the construction industry in the world were associated with the fall of people and equipment from heights. The results of Halabi highlighted that the proportion of fall accidents increased on construction sites. Besides, most of the fall accidents were (1) from heights less than 9.15 m, (2) among the roofers, (3) occurring on new buildings and residential projects with low cost, (4) during the time intervals of 10 : 00–12 : 00 and 13 : 00–15 : 00, (5) among older and untrained workers. This is consistent with the results of the present study [35]. In this regard, special attention is needed to the element of safety-related training. More importantly, selecting people following the assigned job duties is one of this field’s most crucial control strategies [36].

The risk assessment results of the electric shock event in this project illustrated that the risk level of all risk source were at tolerable level (level 2) and need corrective action soon. Previous studies have also shown that paying attention to risk factors related to electrical equipment and appliances and performing control measures such as using earthing systems, using specialized workers, and following safety rules in cabling inside the workshop, mobile wires, electrical switchboards can be a practical step in reducing accidents in construction projects [37]. Lombardi et al.’s study showed that a high number of accidents, especially in construction sites, were due to exposure to electrical hazards (such as electric shock), which is consistent with the results of the present study [38].

Findings from the crane/load and elevator fall risk assessment in the studied construction project showed that all eight sources of risk identified for these two events were at a tolerable risk level and need corrective measures in the near future, which indicates the need for special attention to the risks of this section. The study conducted by Hamid et al. also revealed that the lack of proper use and compliance with the criteria for the use of cranes and elevators in construction projects are among the most critical parameters in occupational accidents in various working environments, and measures such as regular inspection of the structure of the equipment as well as proper training of relevant workers are one of the most important control measures [39].

The soil fall and excavation wall risk assessment results showed that the non-observance of safety principles during excavation to strengthen the excavation wall was at an unacceptable risk level. Based on the findings, it was found that there is the highest risk index in the excavation component and this stage of construction projects requires the highest levels of safety and preventive measures. Previous studies have shown that despite many accidents in the excavation phase due to non-compliance with safety principles and significantly strengthening the walls during the excavation process, implementing appropriate risk assessment methods in this phase is still neglected [40].

Many studies have been conducted to describe the set of activities and tasks in construction projects and identify various individual, occupational, environmental, managerial, and organizational risk factors affecting occupational accidents in these industries with a retrospective approach [41 –43]. However, few studies have been conducted in developing specialized methods of risk assessment following the nature and unique characteristics of construction projects in different countries [44, 45].

4.1 Study strengths and limitations

The present study has been conducted for the first time to implement a new method to assess construction projects’ safety risk and accordance with the dynamic and specific characteristics of construction projects and activities. This study identified the most critical factors affecting occupational accident frequency and severity in construction projects. The present method can be a helpful step toward reducing occupational accident risk levels in the construction industry and developing control plans, especially in developing countries, due to lower risk management performance.

Among the limitations of the present technique is the lack of a quantitative method to calculate and evaluate the effective parameters on the probability and severity of risks in the construction industry. Therefore researchers in the future are recommended to develop and apply quantitative methods with the same algorithm as the present study and according to the conditions of using safety management systems.

It should be mentioned that since the present study was conducted in Iran (a developing country) and the safety levels observed in the construction industry in developed countries are much higher, it is suggested to use this method in these countries with caution. It is also recommended that researchers in developed countries conduct studies in the future using a similar algorithm.

4.2 Future research

Despite the efforts made in the present study to provide a comprehensive and specific method to improve construction projects’ safety levels, given the importance of the risk management process in this industry and the high accident rate, researchers in the future are recommended to develop and apply quantitative methods with the same algorithm as the present study and according to the conditions of using safety management systems with emphasizing proactive approach.

5 Conclusion

The results of this study showed that the risk levels in the studied construction project were tolerable and unacceptable and required corrective measures. The findings of the obtained model in this study demonstrated that using parameters that determine the probability and severity of risk according to the nature of the working environments can be a practical step in evaluating the sources of risk and implementing effective control measures.

Conflict of interest

The authors declare that there is no conflict of interest with respect to the research, authorship, and/or publication of this article.

Ethical approval

Not applicable.

Footnotes

Acknowledgments

The authors are grateful for the cooperation of the management of the studied construction project and the construction and safety experts participating in this study. The present paper is the result of a research project (code 971000, ethical code IR.MUQ.REC.1398.108) approved by Qom University of Medical Sciences.

Funding

This study received no funding.

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