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Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions

GETEC Research Group, Department of Engineering, Pontifical Catholic University of Peru, Av. Universitaria 1801, Lima 15088, Peru
Author to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2023, 20(4), 3412;
Received: 25 October 2022 / Revised: 12 February 2023 / Accepted: 14 February 2023 / Published: 15 February 2023
(This article belongs to the Special Issue Risk Assessment for Occupational Safety and Health)


It is common for companies that are in the process of implementing the Last Planner System (LPS) journey to attempt an increase in productive work and a reduction in waste, such as contributory and noncontributory work. Even though the LPS has proven to have a synergy with the health and safety requirements, companies with deficient health and safety management systems tend to classify work involving substandard acts or conditions as standard, and then pretend to benchmark against other companies that are indeed performing safe work. The following work introduces a framework to simultaneously register and analyze productive, contributory, and noncontributory work, with the substandard acts and conditions in a construction site, allowing for the measurement of production and health & safety indicators simultaneously. In the absence of technology that automatically captures these indicators, it is proposed that simultaneous measurements be made through direct inspections and photo and video recording by means of a handheld camera. The proposed continuous improvement framework follows the steps indicated below: (1) defining the productive, contributory, and noncontributory work with surveys performed on the most representative stakeholders of the industry; (2) proposing a new classification of production and safety work; (3) assessing the level of application of the LPS in the company; (4) measuring the indicators; (5) improving the use of the LPS and performing new measurements; (6) statistically linking deadly, serious, and minor accidents, standard and substandard acts, standard and substandard conditions, and productive, contributory, and noncontributory work. This framework was applied to a case study of a building project in Lima and the results were improved simultaneous indicators, especially the health and safety indicators. Automated classification of productive and nonproductive work using technology still represents a challenge.

1. Introduction

Lean construction can be defined as the adaptation of lean manufacturing or Toyota Production System (TPS) to construction projects, it is based on the participants’ collaborative planning while applying concepts and principles aimed at the reduction of losses (waste), the generation of value for the client and stakeholders, and the continuous improvement of processes and flows [1]. Lean manufacturing could not have been conceived without the prior development of a safe system, rooted in the 5S philosophy, and a drive for normalization and standardization, which obviously includes safety practices. From the beginning, the makers and followers of the lean construction philosophy, starting with Lauri Koskela, included these precepts, the 5S, standardization, safe work, etc. [2]; a mindset ingrained in developed countries and the best worldwide companies, regardless of their origin. It is inconceivable that companies intend to generate value, eliminate waste, and collaboratively plan different activities, without first ensuring a reliable system based on respect for human life.
The last planner system (LPS) is a flexible production planning system that integrates support areas and is designed to generate a predictable workflow and quick learning in all phases of a construction project [3]. LPS allows for the implementation of the lean construction philosophy [1].
There is evidence that proves that the last planner system integrates production, safety, and health in an optimum way, improving the indicators of direction and management, and the indicators of occupational accidents [4,5,6]. We can state that LPS has synergy with safety and health systems, which are compatible with OHSAS 18001:2007 standard “Occupational Health and Safety Assessment Series” [7]. In Peru, health and safety laws have a structure similar to that of the OHSAS 18001 [8]. Since 2018, the International Standards Office has replaced OHSAS 18001 with ISO 45001:2018 standard “Occupational health and safety management systems–Requirements with guidance for use” [9]. It is expected that LPS will also be compatible with ISO 45001 and Peruvian health and safety laws. These systems need an effective method to move from planning into implementation and operation, verification, and revision by direction. This method can come from the evident synergy that exists with LPS. The simultaneous measurement of productivity and safety indicators at minimum cost is advisable.
In emerging and third-world countries, it is common to find deficient health and safety management systems in construction companies. For example, in Peru, many companies begin the Lean Journey without first implementing a correct safety culture [10,11]. On the other hand, they do not even have official statistics such as safety indicators. The Peruvian Ministry of Labor only records the accidents, incidents, and illnesses reported by companies as some sort of affidavit, however, they are not connected to the number of workers or man hours [12].
Benchmarking means researching to find and apply the best practices of companies worldwide [2]. With questions such as: “how did this competitor achieve better indicators than our company? Is trying to access their good practices legitimate, without being considered industrial espionage?”. Companies with high standards have the good practice of measuring indicators to compare performance between different projects to compare themselves with their competitors, promoting continuous improvement [11,13]. Evidently, the strengths and weaknesses of the company must be previously evaluated.
Furthermore, the capture, integration, processing, and analysis of work data to measure productivity, performance, and work categories, among others, is a challenge for construction companies [14,15].
Work sampling (WS) is a technique used by researchers to define and understand the types of productive work of workers on project sites [16]. However, there are still variations and discrepancies between authors [17]. For instance, [18] defines indirect work as talking, preparation, and transportation, while [19] classifies them as preparation, work supplements, administrative, and unusual elements. WS helps the contractor to evaluate the productivity rate, identify the reasons for noncompliance, take corrective actions, reduce waste, and improve performance [20]. However, the measurement of WS indicators has not yet been considered simultaneously with safety indicators. The main purpose of this study is to present a framework that allows the measurement of productive, contributory, and noncontributory work with substandard acts and conditions simultaneously. These new definitions will allow benchmarking between companies. Also, the current state of technologies that allow the simultaneous measurement of these indicators is reviewed.

2. Production Systems

2.1. Work Sampling (WS)

WS consists of performing on-site observations and analyzing their results to establish what the individual workers are doing during specific time frames [21,22].
Before 1985, WS studies adopted the classification of two categories: direct work (DW) and nondirect work. DW is related to value-adding work time [23]. However, the lack of consensus created various subcategories of nondirect work [17]. After 1985, most researchers applied two additional categories, supportive work and waste time, which eventually evolved into indirect work (IW) and waste work (WW) [17,23]. IW could be defined as necessary and supportive work for DW. WW is a work that is not necessary [23]. In Latin America, the use of the productive work (Direct Work), contributory work (indirect work), and noncontributory work (Waste Work) categories is deeply rooted [24]. In this study, Latin American denominations will be used because they are commonly applied in our work (productive work (PW), contributory work (CW), and noncontributory work (NCW)).
The activities are registered onsite through videos and photos for posterior analysis using WS [22]. This approach allows measuring the level of activity in an operation [24], providing a snapshot of the circumstances in which the measurements were performed [22]. Using a representative sample large enough to be statistically sound, it is possible to predict a specific characteristic in an element within a project, or the project as a whole. Even though the prediction is not exact, the results are accurate enough to simulate the real situation, analyze it, and take corrective actions. It is important for the sample to have the following consistency characteristics: (1) the condition of each inspected unit must be independent of the conditions of the other units; (2) each unit must have the same probability of being selected; (3) the basic characteristics of the batch selected for sampling must remain constant [22].
The method of proportion estimation is used to measure the degree of certainty of the sampling process since the obtained results can be expressed as proportions. According to [24], the probability of occurrence of an event can be estimated using Bernoulli’s sequence, as a proportion of the occurrences of said event, in which X1, X2, …, XN, are N independent tests, and each Xi is a random variable that can take the value of one when the event takes place, or zero when the event does not take place, in test i. Thus, the parameter P, corresponding to the probability of occurrence of the event in a test, can be calculated using Equation (1).
P = 1 N i X i
According to the central limit theorem, in which for a large N, P has a normal distribution, and from the confidence interval, the range of error on each side can be calculated using Equation (2) [24]. Statistically, the sample can be validated from three concepts: confidence level, margin of error, and proportion per category. The first one provides the reliability of the result, the second one gives the accuracy of the estimated value, and the last one supplies the expected proportion in the sample. In other words, how the sample responses are distributed. The number of samples for the required conditions can be calculated using Equation (2) [22].
N = k 2 P ( 1 P ) L 2
L = range of error on both sides;
N = number of tests (observations);
k = value of the standard normal variable for a confidence level.
The expected distribution between productive and nonproductive work (direct and nondirect work) is 50:50. Similarly, it is considered acceptable to have a level of confidence of 95%, and a margin of error of 5% to represent the work distribution for an entire project. This can be achieved using 384 samples [22].
In different projects studied in Peru, the professionals in charge defined PW, CW, and NCW differently. Thus, the obtained measurement could not be compared [11]. In other words, the tasks must be defined in the same way to achieve benchmarking.

2.2. Crew Balance Chart

Crew balance charts are the “man–machine charts” from industrial engineering, adapted to the construction sector [22]. They provide an effective way to show the relationship between the activities of the members of a crew, and the equipment they use. To make a balance chart, it is necessary to observe and measure the time used by each worker and machine, on each task of an activity. Ideally, times must be measured in several work cycles, to validate their accuracy and variation during the cycles [22,24]. The project activities are registered through videos and pictures using the Crew Balance chart [22].

2.3. Classification of the Production Work and Benchmarking

Work performed by workers and equipment can be classified into three categories [24,25]: (1) productive work (PW): it contributes directly to production and generates progress; (2) contributory work (CW): it must be carried out so the PW may be executed; it does not generate progress, however, it is necessary. It also does not provide value for the client directly; (3) noncontributory work (NCW): it does not generate progress and it is not necessary; it has a cost and falls directly in the waste category.
It is essential to define each task as PW, CW, and NCW, and to ensure that these definitions are equivalent when benchmarking. For example, in Peru, there are different definitions for the same task, which yields erroneous conclusions when comparing companies [11]. There is no standard that defines each type of work. Thus, it is not possible for companies to benchmark against each other, since the classification of one activity can vary from company to company, or even between projects. What is considered CW, could be considered NCW in another company, and so on. The need to define a standard is established, so that benchmarking is possible as they do in first-world companies.
It is common for companies beginning the lean journey to attempt an increase in productive work and a reduction in waste [26]. This approach boosts the productivity indicator, especially in activities with high incidence in cost, repetitive, critical, or with low productivity levels. The most commonly used sampling techniques to measure the PW, CW, and NCW percentages are by work sampling and a crew balance chart [22,24].

2.4. Proposed Survey to Benchmark the Types of Activities

The sample size was determined based on [27]. Equation (3) determines the size of the sample n based on the following parameters: Z = 1.96, corresponding to the number of standard deviation of the normal distribution based on the level of significance adopted of 95%; the universe size N was the number of building projects built [28]; ε = 5%, is referred to the maximum error acceptable; and p = 50%, considering that there were no previous estimations for none of the selected definitions [27,28].
n = Z 2 p ( 1 P ) N ( N 1 ) ε 2 + [ Z 2 p ( 1 p ) ]

2.5. Last Planner System (LPS)

LPS was developed by Glenn Ballard [29], who stated: (1) planning should be considered as a system, and not based only on the skills of the professionals in charge of programming; (2) the performance of the planning system must be measured; (3) errors in programming must be analyzed, the root causes of these errors must be identified, and corrective measures must be adopted, then results must be evaluated [30]. LPS states that the further the prediction, the more inaccurate it will be [29], so the system gives the following recommendations: (1) during planning, the level of detail of the task should be increased as the date of its execution approaches; (2) planning in a collaborative manner with all project stakeholders, including support areas, such as health and safety, logistics, and quality, among others; (3) opportunely identifying constraints and enforcing their requirements to execute planned assignments as a team; (4) making reliable promises; (5) learning from the interruptions [3,29]. By this, the variability is reduced, and the activities are achieved more efficiently. The LPS elements are (1) master planning (master scheduling): deadlines and milestones are established in the general schedule, and a list of tasks is determined by selecting the construction processes according to the budget and supplies, labor, and available equipment [29]; (2) pull planning phase session: it is a meeting where all the areas involved in the execution of the project have to identify the “handoffs” to be done between all participants, meaning, they are part of the design of the different alternatives to the schedule. The sectorization consists of the team dividing the measurements of all the activities (processes) of one building in a number of sectors in order to create a balanced production line, with resources (workforce, equipment and machinery, and materials, among others) that can be executed in a workday and that enables the correct conditions of everyone involved [31]. All planners must identify the logistics among tasks by adjusting their sequential schedule. These agreements are as compromising as a contract [32]. The attendance and participation in these sessions must be agreed upon in the contracts with the subcontractors [33]; (3) look-ahead planning: the look-ahead plan is usually between two and eight weeks long for building projects and it must be developed and communicated so that everyone involved is aware of the activities scheduled [29]; (4) constraint analysis: when scheduling the activities in the look ahead, an analysis is done so that there are no impediments to its completion. This means it is free of constraints that might generate a breach in the flow, waste, and delays. The constraints can be defined as prerequisites for an activity that, if not covered on time, might produce delays in the production flow [11]; (5) weekly work planning (weekly programming): we must prioritize compliance with the first week of the lookahead, use buffers according to variability and complexity, and provide alternate tasks to execute in case of unforeseen events [29]; (6) daily programming: a very important reason to have a daily program is to make performance measurements, not just of the working crew, but of each of the personnel members, making sure if a worker is productive or not and evaluating if the person has the adequate tools, as well as checking which factors are influencing their productivity, such as health, weather, lack of water, bad eating habits, demotivation, lack of safety planning, etc. [10]; (7) learning (reliability analysis): measurement of the planning system’s performance with the percentage of plan completed (PPC): LPS measures the performance of the weekly plan through the completed task (assignment) percentage (PPC), which is the number of accomplished items divided by the number of programmed tasks (assignments) for any given week. The reliability analysis is the exercise through which we can measure the quality of the programming. Root causes that have hindered achieving the 100% fulfillment of the weekly plan (PPC) can be identified and attempts can be made to eliminate them [29].
In recent years, LPS has been implemented by some contractors in Peru, however, its full potential has not been developed yet [34].

3. Health and Safety Systems

The leadership and participation of workers have become essential for health and safety management systems. For instance, the International Labor Organization (ILO) and the World Health Organization (WHO) urge their member countries to include workers as key participants in management systems in their regulations [35,36]. Coincidentally, in 2018 the ISO published ISO 45001 requiring companies to give workers a leading role in the review and approval of health and safety management systems, as a strategy to reduce and eliminate occupational accidents and illnesses. It is very important to include workers and other stakeholders in the planning meetings [9]. In the same sense, the Agile Practice Guide [37] indicates that lean thinking is a superset, sharing attributes with agile and kanban, modern methods that emerged in the mid-2000s that also promote teamwork to organize safe work areas. LPS is also a modern method focused on teamwork. Its structure is based on lean thinking [1] and is synergistic with safety management since it is based on respect for people [5]. Therefore, the inclusion of all stakeholders in these collaborative meetings cannot be postponed.
Additionally, a study determined that the project and firm-related factors are the most influential in promoting the effectiveness of health and safety training sessions among the success factors that promote health and safety performance. This group consists of variables, such as project type, project size, project duration, and firm size [38]. Consequently, it would be an excellent practice for companies dedicated to the execution of similar projects to benchmark by exchanging their good practices in health and safety training sessions.
Health and safety management systems are based on the evolution of the accident causation theory of Herbert W. Heinrich [7] and immediate causes, basic causes, and operational control failures are defined as the root cause of accidents [39]. In turn, the immediate causes can be classified as substandard acts and conditions. The basic causes can be classified as work factors and personal factors. In several countries, safety regulations are based on these concepts [7]. For example, in Peru, [40] it defines, amongst other concepts, the following: (1) personal factors: related to limitations in experience, phobias, and stress affecting the worker; (2) work factors: related to the work itself, as well as the work conditions and environment; (3) standard act: any safe action or practice executed by the worker; (4) substandard act: any incorrect action or practice executed by the worker; (5) standard condition: any safe condition in the work environment; (6) substandard condition: any condition in the work environment that may cause an accident.
In summary, two types of causes can be defined: due to the employer’s responsibility, and due to the worker’s responsibility. If, and only if, the employer has verified the personal factors of the work applicants, provided training and education to the workers, and has given them the proper personal and collective protection gear, accident causes could be considered exclusively as the worker’s responsibility. In any case, the workflow could be halted due to supervision orders, incidents, accidents, or illnesses. Workers’ behavior can be studied using different management tools and techniques [10,41,42]. For example, behavior-based safety (BBS), as its name indicates, considers the safe behavior of workers as the basis of health and safety management [43]. BBS aims at identifying and modifying the worker’s unsafe action by means of a combination of observation, feedback, training, and goal setting. In addition, BBS has an inverted pyramid approach where the role of the worker is fundamental [44]. We can state that BBS consists in measuring and analyzing the indicator of substandard acts and conditions. These are performed through site inspections with trained staff, able to determine how each worker is operating, and under which work conditions.
Also, there are company policies contractually accepted by their workers. Companies can include penalties for workers committing substandard acts in their internal regulations [45]. Obviously, these substandard acts generate waste in companies and production flow standstills. Not only the worker, the entire crew is involved, as well as the subsequent activities. If the company has not secured in their staff trained workers that can replace the offender, these acts can also generate work stoppages with severe financial waste.
As previously stated, the LPS and the health and safety systems are synergic since there exists evidence of improvement in the safety indicators when both systems are applied simultaneously. For this reason, our research is focused on projects that implement LPS.

4. Measurement of Productive, Contributory, and Noncontributory Work with Substandard Acts and Conditions Simultaneously

Due to the simultaneous record of work types, workers’ act types, and site conditions, there is a classification of production and safety work, as shown in Table 1 [11]. Evidently, productive, contributory, and noncontributory works are valid and comparable only when they comply with standard safety acts and conditions. On the other hand, there are nine work classes (numbered 2, 3, 4, 6, 7, 8, 10, 11, and 12) that can produce the aforementioned waste. These types of waste can pass undetected in companies with deficient safety systems, or even worse, be deliberately ignored in order to create false production indicators aiming to artificially increment their productive work. Figure 1 shows two examples of classified work.
Figure 1 shows two examples of work classification: (a) standing worker (NCW-SA-SSC): this action can be defined as noncontributory work since it is located on solid ground, it is a standard action, and as the surrounding work area is disordered, it can be defined as substandard conditions; (b) using scaffolding (CW-SA-SSC): this action can be defined as contributory work since it is located on a solid platform, it is a standard action, and as the surrounding work area is disordered, it can be defined as substandard conditions.
Additionally, in case of an accident or illness, this would have a financial impact that could, in turn, be subdivided into direct and indirect costs [46]. These direct and indirect costs can be defined as follows: (1) direct cost: expenses generated by the accident such as compensation payment, medical, pharmaceutical, and transfer expenses. This cost is easy to calculate since it is a percentage of the contribution received by each worker. It is paid as a company and employee contributions to the Work Accident Liability Insurance Associations, and they finance the compensations and other expenses; (2) indirect cost: expenses generated by the accident that are difficult to calculate, such as wage costs, extra expense due to increased staff management, material costs, expenses endured by the worker, expenses endured by the company, and expenses endured by society. Despite not having precise costs, it is possible to estimate comparative states of accident rates if the same system is used in all cases.

5. Simultaneous Recording

As previously stated, to apply the work sampling or crew balance chart tools, the tasks are registered through videos and photos for posterior analysis. Also, the safety inspections could be registered using the same technology. Additionally, when films or videos are analyzed, there is the advantage that the results of the evaluation can be reviewed, understood, and audited transparently by any stakeholder [22].
However, is it possible to automate the information processing according to the new classification of production and safety work?
Computer vision and sensor-based technologies are mostly used by researchers, being able to automate data collection for work sampling and activity analysis, measure inputs, outputs, and cycle times, and monitor factors that can have an impact on the productivity and safety of workers [47].
The level of complexity of image processing increases as more people are involved in the construction process. Turaga et al. define two levels of complexity [48]: (1) actions: which are conducted by a sole person and are characterized by simple movement patterns, and (2) activities: which are actions coordinated and executed by small groups of people, and, therefore, they are more complex than an action [48]. This has not changed to this day; it is a technological application that is under development. According to Rao et al., vision-based technologies have had good results in health and safety management systems, detecting people who are close to hazardous areas, and supervising the conduction of safe work, among others [49]. In that sense, in a study developed by Khosrowpour et al., a vision-based technology system is used to detect the position of workers and classify their work with an average accuracy of 70% of the detected positions [50]. However, it is assumed that the position of the worker implies that they are doing a type of work, without distinguishing whether they are doing productive or nonproductive work, for example, standing around doing nothing. Detection of fine motion remains a challenge for video-based technologies. Pose estimation techniques are widely used in ergonomics studies, however, these still need to be improved to determine the categories of productive work [47]. Furthermore, there is a study in progress that analyzes the opportunities of combining data from geographically located observations of workers with data obtained from WS [51,52]. However, there is no further information on whether it could be implemented in real time. Automated classification of productive and nonproductive work using technology still represents a challenge [47,53].
The efforts described in the lines above are important, however, it has been determined that there is still a lot of work to be done to accomplish the automation of the measurements of productive, contributory, and noncontributory work, and further, the automation of these measurements including standard acts and conditions simultaneously.
According to this, this research study is mainly focused on the use of hand-held cameras as a method for capturing photographic and video material. The use of them is selected since there is no technology that can automatically identify and classify these types of work. This will allow us to subsequently review the information collected on site, to have exact and statistically valid measurements. In compliance with the law, the workers were asked by company executives and they agreed to be photographed and filmed. The company already used an inclusive collaborative method in its work, which supported this acceptance.
Since the intention is to use a simple and representative methodology to simultaneously measure production and safety, our proposal involves using work sampling and safety inspections. This will allow the registration and analysis of productive, contributory, and noncontributory work, as well as substandard acts and conditions, at the same time. Balance charts would imply larger efforts and more opposition towards implementation from the interested parties.
With this purpose, it is essential that the inspection staff is properly trained and educated on safety and production work classification. If the company already has a team trained to measure safety indicators, it would be convenient to prepare them for production, and vice versa. Also, the frequency of these simultaneous measurements would need to be decided. While the health and safety indicators are measured daily, the time dedicated to classifying productive work could generate delays, and therefore, additional general expenses. Therefore, the idea is to measure as little as possible and to maintain efficiency levels.

6. Proposed Methodology for Statistical Correlation between Accidents and Type of Work

Ever since Heinrich published his famous 300-29-1 model (300 Near misses and 29 Minor Injuries per 1 Major Injury) [54], many methodologies have been proposed to connect accidents and incidents [46]. Accidents occur due to human factors and mechanical and environmental factors, and more systemic research models are required [55]. However, the scope of this study considers the statistical information of the research already conducted and reported according to the methodologies promoted in the country of the case study. Making an analogy with the Heinrich model, we propose to link fatal, serious, and minor accidents, and the estimated man-hours of each type of work within a timeframe, for example, one year. Statistical correlations between occupational accident rates and the productive, contributory, and noncontributory work of the company can be simultaneously obtained work by work, or by accumulated work, investing the least number of resources and, therefore, using a more economical method. In addition, the quality of the information will be improved, since by making measurements with integrated indicators, the uncertainty of making measurements separately and with no standard methods, with greater deviations and, therefore, with higher costs, will be reduced. According to this, the proposed methodology for statistical correlation consists of:
Step one: representative work sampling in a project during a set timeframe, for example, one calendar year. Microsoft Excel is used to process this data.
Step two: collection of the cumulative percentages of each work type in the sampling.
Step three: estimation of the number of man hours assigned to each type of work within a certain timeframe, for example, one calendar year. According to regulations [40,56], all employers must record and report to the Ministry of Labor fatal, serious, and minor accidents, the number of workers, and the number of man hours per month, per year, etc. This study proposes that the cumulative percentages of each type of work be linked to the total man hours in the same timeframe, in order to calculate the man hours on each type of work. Microsoft Excel is used to process this data.
Step four: To link the fatal, serious, and minor accidents, and the estimated man hours on each type of work within a timeframe.
Step five: Calculate in a simple manner all the relations or indicators required, in addition to the conventional accident rates.
Step six: To build models similar to Heinrich’s to show the proportion of the different types of accidents and types of work.

7. Simultaneous Measuring Framework Proposal for Productivity and Safety

Construction project management systems can be compatible with each other by flexibly adapting sequences and processes, and combining their tools and techniques [57]. According to this, the following framework is proposed:
Step one: survey performed to benchmark the types of activities: Definition of the work performed by the workers according to the categories of productive, contributing, and non-contributing work. This definition is obtained through a survey performed on several experts on the subject. The survey design considers the described by [27,28].
Step two: choosing a project for the case study.
Step three: evaluating the level of implementation of the LPS on the study case project.
Step four: work sampling and simultaneous evaluation of work type and safety inspections and the design of the work sampling. Simultaneous evaluation of work type and safety inspections, assessing the work environment conditions and the type of acts of the workers. Video-recording of these acts to provide evidence of the unbiased evaluations required by this method. Microsoft Excel is used to process this data.
Step five: implementation of safety and production corrective measures: worker re-training after a substandard act. Change a substandard condition to a safe one. Analysis of the obtained results according to the new classification of production and safety work proposed in this paper. Introduction of the production corrective measures derived from this analysis and applying last planner techniques during the meetings to improve the indicators. Measuring the indicators based on the corrective measures.
Step six: statistical correlation of fatal, serious, and minor accidents and types of work: apply the proposed methodology. Microsoft Excel is used to process this data.
Figure 2 shows the flowchart of the research methodology.

8. Results and Discussion

8.1. Survey Performed to Benchmark the Types of Activities

The research universe was composed of civil engineers and architects that work in the construction of buildings of over five stories. Equation (3) determines the size of the sample, n, based on the following parameters: Z = 1.96 (number of the standard deviation of the normal distribution based on the level of significance adopted of 95%); the universe size N was the number of building projects built in Lima and Callao between August 2015 and July 2017 that have an elevator [58]; ε = 5% refers to the maximum error acceptable; and p = 50%, considering that there were no previous estimations [27,28]. After applying these parameters to Equation (3), the number of obtained interviews needed was 315 in the universe of 1738 projects. After verifying the integrity of the data, 334 surveys were performed, those interviewed were civil engineers or architects that worked on different study projects between August 2015 and July 2017 (Table 2). Each professional assessed had to classify a list of 128 activities in terms of productive, contributory, and noncontributory work. The result of this assessment was used as a guideline to standardize the classification of the activities. Although the profile of the respondents is optimal, similar scores could be obtained in some work classifications. As one of the objectives of this study is to do benchmarking, the researchers and the collaborating company agreed that the criteria to define the classification would be by simple majority.
The results of this survey were grouped into 46 types of activities as shown in the table below (Table 3). For example, the placement of vertical and horizontal reinforcement was grouped under the activity placement of materials.
The 128 activities can be used to analyze similar projects but for these case studies the summarized list of activities was chosen.

8.2. Choosing a Project for the Case Study

The case study belongs to a large real estate company with 18 years of experience building massive housing and office projects. Since 2011, it has been associated with the Lean Construction Institute based in Peru, and, therefore, it benchmarks with similar real estate companies, sharing its tools, techniques, and good practices, such as safety training strategies, which are essential for good performance in occupational accidents, according to [38]. In compliance with Peruvian law, the worker agrees that at any time during the investigators’ visit, the employee’s work may be photographed or videotaped by the researchers for research purposes.
This project was a 15-story residential building of 190 apartments, made of reinforced concrete. It was monitored through a hand-held camera which allowed for effective work sampling. The equipment used in the study was a Canon Powershot A2300, with a 16.0 MP Image Sensor, DIGIC 4 Image Processor, 5x Optical Zoom, 720p HD video recording and 16 effective megapixels.

8.3. Evaluating the Level of Implementation of the LPS on the Study Case Project

A total of 12 surveys were performed on two project managers, two field engineers, two technical office managers, two administrators, two safety supervisors, and two quality assurance engineers. The level of LPS implementation is shown in Table 4.
It was observed that the company’s initial implementation of the LPS was incomplete. It should be mentioned that collaborative safety planning sessions, five why analysis, and corrective measures were not entirely performed. In other words, the field engineers were not working with their support areas, especially, safety and health supervisors. This generated substandard acts and conditions that may be avoided if every worker in the project was aligned with safe and collaborative work. Thus, the missing LPS elements must be implemented. This project had an accumulated PPC of 81%, and even though this is a relatively high percentage, it may be affected by the incidents or accidents waiting to happen.

8.4. Work Sampling and Simultaneous Evaluation of Work Type and Safety Inspections

A work sampling was designed to achieve a minimum level of confidence of 95%, and a margin of error of 5%. The minimum number of samples needed for this purpose was 384 [22].
Four independent measurements were performed on 101 workers, obtaining 404 valid samples. The work type assessment and the safety inspections were executed simultaneously. The evaluations were video recorded. Table 5 shows the work sampling integrated with the safety classification.
Table 6 shows the summary of this evaluation and four video snapshots and their work classifications.
Corrective measures were taken, and a second assessment was performed to measure the improvement onsite. The obtained results were analyzed and shown in Table 7.

8.5. Implementation of Safety and Production Corrective Measures

Corrective measures were given in the form of retraining for workers from point one forward. Therefore, the improvement of safety indicators was accomplished since there is a synergy in the simultaneous measurement of both. Table 8 shows the summary of this evaluation and the improvement in the acts and conditions.
It is important to mention that the company has now implemented all the elements of the LPS, meaning there are pull planning sessions, collaborative planning sessions, five why analyses, and corrective measures adoption. Moreover, the field engineers are working together with the support areas, including the safety supervisors, as a team. There were no major setbacks and everything went according to plan. What improved, ostensibly, were the health and safety indicators.
According to the company data, the percentages of PW, CW, and NCW were normal. On the other hand, it can be observed in Table 6 and Table 8 that work with substandard acts decreased from 155 (38.4%) to 66 (16.3%). Further, it shows that work with substandard conditions decreased from 24 (5.94%) to 0%, among others. It is important to mention that training based on the staff’s behavior was reinforced. With this, the following measurements stayed within the standard conditions and the substandard acts were even further reduced. On the other hand, this project improved its weekly PPC to 86% and its accumulated PPC to 82%, which are similar values to the initial ones. However, the likelihood to have an incident or accident was reduced considerably. Thus, this will contribute to the safety costs in the mid and long term, and, most importantly, workers and third parties will be protected. Finally, and given the lack of explicit regulation, with a lean system, the civil and criminal responsibility of the involved agents would be covered in a better manner [59].

8.6. Statistical Correlation of Fatal, Serious, and Minor Accidents and Types of Work

For educational purposes, this study performed a simulated application of the methodology, considering that the percentages shown in Table 9 depict the representative measurements in a year.
For confidentiality reasons, the company did not provide its accident statistics. On the other hand, Peru does not count with official statistics for accident rate indicators that could be used to simulate a correlation with Peruvian average values [11,12]. Due to this, and solely for educational purposes, the 2017 official statistics of an important Peruvian company [60] will be used instead, in which a summary by accident is shown in Table 10. It is important to state that this company implements LPS in its building projects, so it is an excellent reference for our research.
Then, Table 9 and Table 10 are statistically linked, and it is determined that for every 17 restricted work cases, there are 30 minor accidents, and the man hours are shown in Table 11.
Based on this information it is possible to construct correlation models similar to the Heinrich model, selecting or grouping the variables as deemed pertinent. For instance, Figure 3 shows a model with the data from Table 10 and Table 11 divided by 17.
In addition, it is determined that the 3828 workers were exposed to a total of 54,567 h of substandard conditions (SSC), thus an average of 14.25 h of exposure per worker. It is also concluded that each worker conducted an average of 1605.20 h of the PW–SA–SC type of work in the year. In the same way, all the relations or indicators required are calculated, in addition to the conventional accident rates, making the correlation proposed in our research original, valuable, and easy to apply.
The proposed framework has the advantage that fewer resources will be used when making simultaneous measurements which are traditionally made separately. When analyzing these indicators in a collaborative environment, work satisfaction increases, which is very common with lean-approach projects. As demonstrated in the study, indicators were improved. However, work classifications and study results could vary according to the cultural level of the workers and professionals, their work habits, engineering and construction processes, industrialization level, and types of contracts, among other factors.

9. Conclusions

This paper presented an application that allowed the measurement of productive, contributory, and noncontributory work with substandard acts and conditions simultaneously in a construction site. In this manner, benchmarking was possible.
The framework proposes a classification of work, measuring these indicators of production and safety simultaneously. Standard and substandard acts; standard and substandard conditions; and productive, contributory, and noncontributory work are statistically connected. To implement the proposed framework, the procedures of the production and the health and safety support areas must be updated, integrating the new approach.
As the case study showed, implementing the last planner system accordingly has an impact, not only on the productive but also on the health and safety indicators. This is accomplished since there is a synergy between the lean construction philosophy and the health and safety management systems. It presents evidence that respect for workers is fundamental to improving the health and safety indicators in construction projects. The behavior of workers, contractors, staff, and investors changed.
Statistical correlations between occupational accidents and productive, contributory, and noncontributory work were obtained simultaneously by investing the least number of resources and, therefore, using a more economical method. The quality of the information was improved by obtaining integrated indicators, which reduced the uncertainty of making measurements separately, without a standard method, and with higher costs. The accidents by category and the classification of work are statistically connected in a simple way thanks to the framework proposed in this research.
This measurement system will allow the benchmarking with projects within the same company, and with other companies applying the same methodology. It is important to compare measurements in the same project phases.
In this research, we requested the express approval of the workers to be photographed and filmed according to Peruvian Law. However, when using other technologies, the legal analysis corresponding to every technology must be conducted.
A proposed future line of research is to automate the classification of the types of work, based on this classification, after gathering the visual information. The combination of several technologies such as sensors, radio-based or vision-based technologies, drones, etc., will present a real challenge.

Author Contributions

X.B.: conceptualization, funding acquisition. X.B. and C.C.-H.: methodology, formal analysis, resources, writing—original draft preparation, writing—review and editing. All authors have read and agreed to the published version of the manuscript.


This research was partially funded by the Department of Engineering at the Pontifical Catholic University of Peru and the Dirección de Fomento de la Investigación at the Pontifical Catholic University of Peru.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data used in this study are available on Table 1, Table 2, Table 3, Table 4, Table 5, Table 6, Table 7, Table 8, Table 9, Table 10 and Table 11.


Natalia Sihuay is thanked for her support in data collection. We would like to thank the company that provided access to the case study.

Conflicts of Interest

The authors declare no conflict of interest.


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Figure 1. (a) Standing worker (NCW-SA-SSC); (b) Using scaffolding (CW-SA-SSC).
Figure 1. (a) Standing worker (NCW-SA-SSC); (b) Using scaffolding (CW-SA-SSC).
Ijerph 20 03412 g001aIjerph 20 03412 g001b
Figure 2. Research methodology.
Figure 2. Research methodology.
Ijerph 20 03412 g002
Figure 3. Correlation Models similar to the Heinrich model.
Figure 3. Correlation Models similar to the Heinrich model.
Ijerph 20 03412 g003
Table 1. Classification of production and safety work [11].
Table 1. Classification of production and safety work [11].
CodeProduction Work ClassesAct ClassesCondition Classes
1PW-SA-SCProductive WorkStandard ActStandard Conditions
2PW-SA-SSCProductive WorkStandard ActSubstandard Conditions
3PW-SSA-SCProductive WorkSubstandard ActStandard Conditions
4PW-SSA-SSCProductive WorkSubstandard ActSubstandard Conditions
5CW-SA-SCContributory WorkStandard ActStandard Conditions
6CW-SA-SSCContributory WorkStandard ActSubstandard Conditions
7CW-SSA-SCContributory WorkSubstandard ActStandard Conditions
8CW-SSA-SSCContributory WorkSubstandard ActSubstandard Conditions
9NCW-SA-SCNoncontributory WorkStandard ActStandard Conditions
10NCW-SA-SSCNoncontributory WorkStandard ActSubstandard Conditions
11NCW-SSA-SCNoncontributory WorkSubstandard ActStandard Conditions
12NCW-SSA-SSCNoncontributory WorkSubstandard ActSubstandard Conditions
Table 2. Results of the survey taken to classify productive, contributory, and noncontributory work.
Table 2. Results of the survey taken to classify productive, contributory, and noncontributory work.
1Placement of horizontal reinforcement32590334
2Placement of vertical reinforcement324100334
3Placement of wire246844334
4Placement of slab form panel273547334
5Placement of formwork accessories in slab2251036334
6Placement of wall form panel267643334
7Placement of formwork accessories in wall2051272334
8Placing of formwork stiffeners2121202334
9Placing formwork struts2231074334
10Pouring concrete316162334
11Leveling concrete2121220334
12Vibrating concrete2211121334
13Installing electric pipes307243334
14Installing rectangular box309250334
15Wall grinding260704334
16Leveling mortar2111203334
17Plastering walls2261062334
18Installing gas pipes307252334
19Fusing water pipes2101186334
20Installation of sewage pipeline285481334
21Brick placement288442334
23Placing wire in masonry walls1791514334
24Laying out1671598334
25Sanding door frame19411822334
26Installing window frame260695334
27Installing drywall profiles268642334
28Installing ceramic tiles293401334
29Placing telecommunications cable256762334
30Installing hinges on door260731334
31Plastering drywall 271612334
32Filling door frame232957334
33Installing wallpaper2606311334
34Placing props in lightened slab formwork2161126334
35Placing beams in lightened slab formwork240922334
36Placing plywood in lightened slab formwork235963334
37Nailing components in lightened slab formwork1661626334
38Adjusting beams in lightened slab formwork1801495334
39Placing precast joist296380334
40Adjusting precast joist247861334
41Placing bricks for lightened slab290422334
42Installing Styrofoam to seal lightened slab bricks2121175334
43Join water pipes 2131192334
44Installing water pipes312220334
45Installing pipe fittings and connectors289450334
46Finding materials4220488334
47Placing separators for concrete10119637334
48Moving to another point to install reinforcement16209109334
50Opening reinforcement packages with a shear826264334
51Transporting material2427931334
52Receiving/Giving instructions2026153334
53Removing wall formwork accessories12919312334
54Removing formwork aligner11021311334
55Carrying tools1127251334
56Removing plywood in wall formwork1212049334
57Finding accessories of slab formwork6212116334
58Removing accessories of slab formwork10921312334
59Removing plywood in slab formwork13019311334
60Applying mold release agent14617414334
61Cleaning formwork3725740334
62Level out concrete with a shovel or foot11918926334
63Carrying material4027024334
64Placing baseboard on one side1651672334
65Giving/Receiving instructions3726235334
66Gathering concrete from the slab to use it in the parapet7922629334
67Removing concrete from formwork using a hammer3425941334
68Placing/removing separators for concrete3827818334
69Cleaning tools324289334
70Cleaning the work area, a day before1525069334
71Removing equipment from the work area 623593334
72Maneuvering mixer or pump to pour concrete11221111334
73Maneuvering pipes, hoses, and accessories11221012334
74Pouring leftover concrete from a slab in a wall9515683334
75Cutting electrical pipes1182079334
76Cutting gas pipes11121310334
77Repairing walls to install pipes12712384334
78Introducing cable guides in electrical pipes1681633334
79Cutting sewage pipes9522910334
80Preparing materials19912510334
81Wet wall for masonry work7624711334
82Placing accessories in wall12320011334
83Assembly of scaffold5926411334
84Water leak test9522415334
86Using lifeline3827521334
87Preparing mortar19512910334
89Transporting cleaning materials1525465334
90Performing a hydrostatic test10221418334
91Installing safety rails6424525334
92Drilling wall for plastering12418624334
93Cutting profiles for drywall1571716334
94Cutting tiles862408334
95Cutting wallpaper6724522334
96Preparing workspace6723928334
97Drilling on demolition debris to make a trench14817016334
98To shovel12616741334
99Transporting objects2927431334
100Transporting materials with a crane2628226334
101Verifying the alignment of the ceiling5925520334
102Set up cutting machine3227131334
103Drilling on melamine cabinets10121023334
104Drilling a slab11918530334
105Repairing a slab75144115334
106Training the crew on safety during construction4425139334
107Receiving safety training3526138334
108Receiving a safety induction because of a substandard act28200106334
109Installing collective protection equipment5924332334
110Safety signs5724532334
111Safety drill3225745334
112Level out1581742334
113Cutting water pipes1102177334
114Measuring onsite8923213334
115Reading blueprints5725324334
116Running QA tests (pressure or water tightness)11320021334
117Preventive maintenance for equipment3526435334
118Corrective maintenance for equipment4220884334
119Going to/coming back from lunch out of schedule1372249334
120Waiting for the concrete bucket to pour concrete1490230334
121Transporting an empty bucket7112215334
123Redoing work (Straightening steel reinforcement)490240334
124Idle time275257334
125Going to the toilette1129204334
126Walking empty handed471259334
127Having breakfast13119202334
128Redoing work1783234334
Table 3. Groups of activities result from the survey.
Table 3. Groups of activities result from the survey.
ItemActivityWork TypeCode
2Application of materialsPWPW02
4Fusion of water pipesPWPW04
7Placement of materialsPWPW07
8Placement of formworkPWPW08
10Preparation of materialPWPW10
11Sand door framePWPW11
12Vibrating concretePWPW12
14Applying mold release agentCWCW01
15Assembly of scaffoldCWCW02
16Carrying material or toolsCWCW03
18Construction site inspectionCWCW05
20Demarcation of work areaCWCW07
22Enable cutting machineCWCW09
23Giving instructionsCWCW10
24Installation of prevention measuresCWCW11
25Lifting equipment with a craneCWCW12
26Maneuvering pipes or accessories to productive workCWCW13
27Moving materialsCWCW14
28Patching wall to install tiles or pipesCWCW15
29Placement of equipmentCWCW16
30Preparing workspaceCWCW17
31Receiving instructionsCWCW18
33Safety supervisionCWCW20
35Taking measurementsCWCW22
38Wet wall for masonry worksCWCW25
39Having breakfastNCWNCW01
40Idle timeNCWNCW02
41Redoing workNCWNCW03
42Standing workerNCWNCW04
43Transporting an empty bucketNCWNCW05
44Unproductive tripNCWNCW06
45Using the restroomNCWNCW07
Table 4. Initial Level of implementation of the LPS of the Project.
Table 4. Initial Level of implementation of the LPS of the Project.
Last Planner System ElementImplementation Rate
Master plan 100%
Health and safety plan100%
Pull Planning Session100%
Percent Plan Completion (PPC)100%
Collaborative Safety Planning50%
5 Why Analysis and Corrective Measures25%
Table 5. Work Sampling based on the new classification.
Table 5. Work Sampling based on the new classification.
ActivityNumberType of WorkType of ActType of ConditionClassification
Brick placement3PWSASCPW-SA-SC
Brick placement2PWSSASCPW-SSA-SC
Filling door frame4PWSSASCPW-SSA-SC
Fusing water pipes2PWSSASCPW-SSA-SC
Installation of elevator3PWSASCPW-SA-SC
Installation of elevator2PWSSASCPW-SSA-SC
Installing ceramic tiles2PWSSASCPW-SSA-SC
Installing electric pipes9PWSASCPW-SA-SC
Installing electric pipes2PWSSASCPW-SSA-SC
Installing gas pipes3PWSASCPW-SA-SC
Installing hinges on door2PWSSASCPW-SSA-SC
Installing horizontal reinforcement3PWSASCPW-SA-SC
Installing profiles for drywall2PWSSASCPW-SSA-SC
Installing rectangular boxes3PWSASCPW-SA-SC
Installing sewage pipes2PWSSASCPW-SSA-SC
Installing wallpaper2PWSSASCPW-SSA-SC
Installing window frame3PWSASCPW-SA-SC
Introducing cable guides in electrical pipes3PWSASCPW-SA-SC
Introducing cable guides in electrical pipes6PWSSASCPW-SSA-SC
Level out concrete6PWSASCPW-SA-SC
Level out concrete3PWSSASSCPW-SSA-SSC
Level out concrete with a shovel or foot2PWSSASCPW-SSA-SC
Placement of wire18PWSASCPW-SA-SC
Placement of wire4PWSSASCPW-SSA-SC
Placing accessories in wall formwork6PWSASCPW-SA-SC
Placing plywood in wall formwork3PWSASCPW-SA-SC
Placing telecommunications cable2PWSSASCPW-SSA-SC
Plastering drywall2PWSSASCPW-SSA-SC
Plastering wall3PWSASCPW-SA-SC
Plastering wall2PWSSASCPW-SSA-SC
Preparing electric material2PWSSASCPW-SSA-SC
Preparing material to install pipes3PWSASCPW-SA-SC
Preparing melamine cabinets2PWSSASCPW-SSA-SC
Preparing mortar2PWSSASCPW-SSA-SC
Sanding door frame3PWSASCPW-SA-SC
Sanding door frame2PWSSASCPW-SSA-SC
Vibrating concrete2PWSSASCPW-SSA-SC
Wall grinding6PWSASCPW-SA-SC
Wall grinding8PWSSASCPW-SSA-SC
Applying mold release agent2CWSASCCW-SA-SC
Carrying tools2CWSASCCW-SA-SC
Drilling on demolition debris2CWSASCCW-SA-SC
Drilling on melamine cabinets2CWSSASCCW-SSA-SC
Erect scaffolding2CWSASCCW-SA-SC
Giving instructions2CWSASCCW-SA-SC
Giving instructions2CWSSASCCW-SSA-SC
Going to the toilette2CWSASCCW-SA-SC
Installing safety rails2CWSASSCCW-SA-SSC
Using scaffolding1CWSASSCCW-SA-SSC
Preparing workspace2CWSASCCW-SA-SC
Receiving instructions4CWSASCCW-SA-SC
Receiving instructions2CWSSASCCW-SSA-SC
Removing accessories in wall formwork2CWSASCCW-SA-SC
Removing accessory2CWSASCCW-SA-SC
Removing formwork struts2CWSASCCW-SA-SC
Removing plywood in wall formwork3CWSASSCCW-SA-SSC
Removing plywood in wall formwork4CWSASCCW-SA-SC
Removing plywood in wall formwork6CWSSASCCW-SSA-SC
Risk Prevention2CWSASCCW-SA-SC
Risk prevention—Securing lifeline2CWSSASCCW-SSA-SC
Running hydrostatic test2CWSSASCCW-SSA-SC
Set up cutting machine2CWSSASCCW-SSA-SC
Transporting material36CWSASCCW-SA-SC
Transporting material8CWSSASCCW-SSA-SC
Transporting materials with a crane2CWSSASCCW-SSA-SC
Transporting objects8CWSASCCW-SA-SC
Transporting objects4CWSSASCCW-SSA-SC
Verifying before wall grinding2CWSASCCW-SA-SC
Verifying the alignment of the ceiling2CWSSASCCW-SSA-SC
Water leak test2CWSASCCW-SA-SC
Wet wall for masonry works2CWSASCCW-SA-SC
Redone work—Drilling on slab3NCWSASSCNCW-SA-SSC
Redone work—Drilling on slab3NCWSASCNCW-SA-SC
Redone work—Drilling wall 3NCWSASCNCW-SA-SC
Repairing slab6NCWSASCNCW-SA-SC
Standing worker12NCWSASCNCW-SA-SC
Standing worker4NCWSSASCNCW-SSA-SC
Standing worker3NCWSASSCNCW-SA-SSC
Transporting an empty bucket2NCWSSASCNCW-SSA-SC
Unproductive trip9NCWSASCNCW-SA-SC
Unproductive trip10NCWSSASCNCW-SSA-SC
Table 6. Application of new classification and video snapshots.
Table 6. Application of new classification and video snapshots.
Table 7. Work sampling based on the new classification after corrective measures.
Table 7. Work sampling based on the new classification after corrective measures.
ActivityNumberType of WorkType of ActType of ConditionClassification
Installing electric pipes17PWSASCPW-SA-SC
Installing electric pipes1PWSSASCPW-SSA-SC
Installing gas pipes5PWSASCPW-SA-SC
Installing gas pipes6PWSSASCPW-SSA-SC
Installing reinforcement15PWSASCPW-SA-SC
Installing reinforcement1PWSSASCPW-SSA-SC
Installing sewage pipeline2PWSASCPW-SA-SC
Installing sewage pipeline3PWSSASCPW-SSA-SC
Installing water pipes4PWSASCPW-SA-SC
Installing water pipes8PWSSASCPW-SSA-SC
Level out concrete1PWSASCPW-SA-SC
Placement of formwork34PWSASCPW-SA-SC
Placement of formwork1PWSSASCPW-SSA-SC
Placing separators for concrete5PWSASCPW-SA-SC
Placing struts in formwork9PWSASCPW-SA-SC
Placing wire15PWSASCPW-SA-SC
Pouring concrete4PWSASCPW-SA-SC
Preparing material13PWSASCPW-SA-SC
Preparing material2PWSSASCPW-SSA-SC
Preparing reinforcement3PWSASCPW-SA-SC
Vibrating concrete3PWSASCPW-SA-SC
Applying mold release agent1CWSASCCW-SA-SC
Assemble scaffolding5CWSASCCW-SA-SC
Cleaning formwork1CWSASCCW-SA-SC
Cleaning reinforcement2CWSASCCW-SA-SC
Giving instructions8CWSASCCW-SA-SC
Giving instructions5CWSSASCCW-SSA-SC
Posting signs1CWSSASCCW-SSA-SC
Transporting formwork2CWSASCCW-SA-SC
Transporting formwork2CWSSASCCW-SSA-SC
Transporting objects1CWSASCCW-SA-SC
Preparing work area to pour concrete2CWSASCCW-SA-SC
Receiving instructions12CWSASCCW-SA-SC
Receiving instructions5CWSSASCCW-SSA-SC
Removing struts 2CWSASCCW-SA-SC
Transporting material48CWSASCCW-SA-SC
Transporting material4CWSSASCCW-SSA-SC
Transporting materials with a crane9CWSASCCW-SA-SC
Transporting objects30CWSASCCW-SA-SC
Transporting scaffolding2CWSASCCW-SA-SC
Unloading joists3CWSASCCW-SA-SC
Redone work—Drilling1NCWSASCNCW-SA-SC
Unproductive trip4NCWSASCNCW-SA-SC
Unproductive trip3NCWSSASCNCW-SSA-SC
Wall grinding8NCWSASCNCW-SA-SC
Table 8. Improvement in production and safety.
Table 8. Improvement in production and safety.
Table 9. Percentages of measurements in a year.
Table 9. Percentages of measurements in a year.
Table 10. Accident rate of a Peruvian construction company [60].
Table 10. Accident rate of a Peruvian construction company [60].
Number of man hours16,535,491
Number of workers3828
Number of restricted work case17
Number of minor accidents30
Number of fatal accidents0
Working days lost due to accidents450
Table 11. Hours worked in a year.
Table 11. Hours worked in a year.
CodePercentageHours Worked
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MDPI and ACS Style

Brioso, X.; Calderon-Hernandez, C. Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions. Int. J. Environ. Res. Public Health 2023, 20, 3412.

AMA Style

Brioso X, Calderon-Hernandez C. Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions. International Journal of Environmental Research and Public Health. 2023; 20(4):3412.

Chicago/Turabian Style

Brioso, Xavier, and Claudia Calderon-Hernandez. 2023. "Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions" International Journal of Environmental Research and Public Health 20, no. 4: 3412.

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