Framework for Integrating Productive, Contributory, and Noncontributory Work...

[Full title: Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions]

Citation: 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. https:// doi.org/10.3390/ijerph 20043412 Academic Editors: Jo ã o dos Santos Baptista, Antonio Jos é Carpio de los Pinos and Mar í a de las Nieves Gonz á lez Garc í a Received: 25 October 2022 Revised: 12 February 2023 Accepted: 14 February 2023 Published: 15 February 2023 Copyright: © 2023 by the authors Licensee MDPI, Basel, Switzerland This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/) International Journal of Environmental Research and Public Health Article Framework for Integrating Productive, Contributory, and Noncontributory Work with Safe and Unsafe Acts and Conditions Xavier Brioso * and Claudia Calderon-Hernandez GETEC Research Group, Department of Engineering, Pontifical Catholic University of Peru, Av. Universitaria 1801, Lima 15088, Peru * Correspondence: xbrioso@pucp.edu.pe Abstract: 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 Keywords: productivity measurements; health and safety measurements; last planner system; health and safety management; workers 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 5 S 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 5 S, 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, Int. J. Environ. Res. Public Health 2023 , 20 , 3412. https://doi.org/10.3390/ijerph 20043412 https://www.mdpi.com/journal/ijerph

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 2 of 24 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 – 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 ].

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 3 of 24 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 X 1, X 2, . . . , 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 Xi (1) 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 (2) where: 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.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 4 of 24 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 )] (3) 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

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 5 of 24 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-2000 s 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.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 6 of 24 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.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 7 of 24 Table 1. Classification of production and safety work [ 11 ]. N ◦ Code Production Work Classes Act Classes Condition Classes 1 PW-SA-SC Productive Work Standard Act Standard Conditions 2 PW-SA-SSC Productive Work Standard Act Substandard Conditions 3 PW-SSA-SC Productive Work Substandard Act Standard Conditions 4 PW-SSA-SSC Productive Work Substandard Act Substandard Conditions 5 CW-SA-SC Contributory Work Standard Act Standard Conditions 6 CW-SA-SSC Contributory Work Standard Act Substandard Conditions 7 CW-SSA-SC Contributory Work Substandard Act Standard Conditions 8 CW-SSA-SSC Contributory Work Substandard Act Substandard Conditions 9 NCW-SA-SC Noncontributory Work Standard Act Standard Conditions 10 NCW-SA-SSC Noncontributory Work Standard Act Substandard Conditions 11 NCW-SSA-SC Noncontributory Work Substandard Act Standard Conditions 12 NCW-SSA-SSC Noncontributory Work Substandard Act Substandard Conditions Int. J. Environ. Res. Public Health 2023 , 20 , x 7 of 25 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. Table 1. Classification of production and safety work [11]. N° Code Production Work Classes Act Classes Condition Classes 1 PW-SA-SC Productive Work Standard Act Standard Conditions 2 PW-SA-SSC Productive Work Standard Act Substandard Conditions 3 PW-SSA-SC Productive Work Substandard Act Standard Conditions 4 PW-SSA-SSC Productive Work Substandard Act Substandard Conditions 5 CW-SA-SC Contributory Work Standard Act Standard Conditions 6 CW-SA-SSC Contributory Work Standard Act Substandard Conditions 7 CW-SSA-SC Contributory Work Substandard Act Standard Conditions 8 CW-SSA-SSC Contributory Work Substandard Act Substandard Conditions 9 NCW-SA-SC Noncontributory Work Standard Act Standard Conditions 10 NCW-SA-SSC Noncontributory Work Standard Act Substandard Conditions 11 NCW-SSA-SC Noncontributory Work Substandard Act Standard Conditions 12 NCW-SSA-SSC Noncontributory Work Substandard Act Substandard Conditions 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. ( a ) Int. J. Environ. Res. Public Health 2023 , 20 , x 8 of 25 ( b ) Figure 1. ( a ) Standing worker (NCW-SA-SSC); ( b ) Using scaffolding (CW-SA-SSC). 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? Figure 1. ( a ) Standing worker (NCW-SA-SSC); ( b ) Using scaffolding (CW-SA-SSC).

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 8 of 24 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 videobased 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

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 9 of 24 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.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 10 of 24 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 retraining 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 Int. J. Environ. Res. Public Health 2023 , 20 , x 11 of 25 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. Figure 2. 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. Figure 2. Research methodology.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 11 of 24 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 Table 2. Results of the survey taken to classify productive, contributory, and noncontributory work Item Activity PW CW NCW Total 1 Placement of horizontal reinforcement 325 9 0 334 2 Placement of vertical reinforcement 324 10 0 334 3 Placement of wire 246 84 4 334 4 Placement of slab form panel 273 54 7 334 5 Placement of formwork accessories in slab 225 103 6 334 6 Placement of wall form panel 267 64 3 334 7 Placement of formwork accessories in wall 205 127 2 334 8 Placing of formwork stiffeners 212 120 2 334 9 Placing formwork struts 223 107 4 334 10 Pouring concrete 316 16 2 334 11 Leveling concrete 212 122 0 334 12 Vibrating concrete 221 112 1 334 13 Installing electric pipes 307 24 3 334 14 Installing rectangular box 309 25 0 334 15 Wall grinding 260 70 4 334 16 Leveling mortar 211 120 3 334 17 Plastering walls 226 106 2 334 18 Installing gas pipes 307 25 2 334 19 Fusing water pipes 210 118 6 334 20 Installation of sewage pipeline 285 48 1 334 21 Brick placement 288 44 2 334 22 Filling 274 57 3 334 23 Placing wire in masonry walls 179 151 4 334 24 Laying out 167 159 8 334 25 Sanding door frame 194 118 22 334 26 Installing window frame 260 69 5 334 27 Installing drywall profiles 268 64 2 334 28 Installing ceramic tiles 293 40 1 334 29 Placing telecommunications cable 256 76 2 334 30 Installing hinges on door 260 73 1 334 31 Plastering drywall 271 61 2 334 32 Filling door frame 232 95 7 334 33 Installing wallpaper 260 63 11 334 34 Placing props in lightened slab formwork 216 112 6 334 35 Placing beams in lightened slab formwork 240 92 2 334

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 12 of 24 Table 2. Cont Item Activity PW CW NCW Total 36 Placing plywood in lightened slab formwork 235 96 3 334 37 Nailing components in lightened slab formwork 166 162 6 334 38 Adjusting beams in lightened slab formwork 180 149 5 334 39 Placing precast joist 296 38 0 334 40 Adjusting precast joist 247 86 1 334 41 Placing bricks for lightened slab 290 42 2 334 42 Installing Styrofoam to seal lightened slab bricks 212 117 5 334 43 Join water pipes 213 119 2 334 44 Installing water pipes 312 22 0 334 45 Installing pipe fittings and connectors 289 45 0 334 46 Finding materials 42 204 88 334 47 Placing separators for concrete 101 196 37 334 48 Moving to another point to install reinforcement 16 209 109 334 49 Measuring 41 271 22 334 50 Opening reinforcement packages with a shear 8 262 64 334 51 Transporting material 24 279 31 334 52 Receiving/Giving instructions 20 261 53 334 53 Removing wall formwork accessories 129 193 12 334 54 Removing formwork aligner 110 213 11 334 55 Carrying tools 11 272 51 334 56 Removing plywood in wall formwork 121 204 9 334 57 Finding accessories of slab formwork 6 212 116 334 58 Removing accessories of slab formwork 109 213 12 334 59 Removing plywood in slab formwork 130 193 11 334 60 Applying mold release agent 146 174 14 334 61 Cleaning formwork 37 257 40 334 62 Level out concrete with a shovel or foot 119 189 26 334 63 Carrying material 40 270 24 334 64 Placing baseboard on one side 165 167 2 334 65 Giving/Receiving instructions 37 262 35 334 66 Gathering concrete from the slab to use it in the parapet 79 226 29 334 67 Removing concrete from formwork using a hammer 34 259 41 334 68 Placing/removing separators for concrete 38 278 18 334 69 Cleaning tools 3 242 89 334 70 Cleaning the work area, a day before 15 250 69 334 71 Removing equipment from the work area 6 235 93 334 72 Maneuvering mixer or pump to pour concrete 112 211 11 334 73 Maneuvering pipes, hoses, and accessories 112 210 12 334 74 Pouring leftover concrete from a slab in a wall 95 156 83 334 75 Cutting electrical pipes 118 207 9 334 76 Cutting gas pipes 111 213 10 334 77 Repairing walls to install pipes 127 123 84 334 78 Introducing cable guides in electrical pipes 168 163 3 334 79 Cutting sewage pipes 95 229 10 334 80 Preparing materials 199 125 10 334 81 Wet wall for masonry work 76 247 11 334 82 Placing accessories in wall 123 200 11 334 83 Assembly of scaffold 59 264 11 334 84 Water leak test 95 224 15 334 85 Measuring 54 256 24 334 86 Using lifeline 38 275 21 334 87 Preparing mortar 195 129 10 334 88 Measuring 42 272 20 334 89 Transporting cleaning materials 15 254 65 334 90 Performing a hydrostatic test 102 214 18 334 91 Installing safety rails 64 245 25 334 92 Drilling wall for plastering 124 186 24 334

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 13 of 24 Table 2. Cont Item Activity PW CW NCW Total 93 Cutting profiles for drywall 157 171 6 334 94 Cutting tiles 86 240 8 334 95 Cutting wallpaper 67 245 22 334 96 Preparing workspace 67 239 28 334 97 Drilling on demolition debris to make a trench 148 170 16 334 98 To shovel 126 167 41 334 99 Transporting objects 29 274 31 334 100 Transporting materials with a crane 26 282 26 334 101 Verifying the alignment of the ceiling 59 255 20 334 102 Set up cutting machine 32 271 31 334 103 Drilling on melamine cabinets 101 210 23 334 104 Drilling a slab 119 185 30 334 105 Repairing a slab 75 144 115 334 106 Training the crew on safety during construction 44 251 39 334 107 Receiving safety training 35 261 38 334 108 Receiving a safety induction because of a substandard act 28 200 106 334 109 Installing collective protection equipment 59 243 32 334 110 Safety signs 57 245 32 334 111 Safety drill 32 257 45 334 112 Level out 158 174 2 334 113 Cutting water pipes 110 217 7 334 114 Measuring onsite 89 232 13 334 115 Reading blueprints 57 253 24 334 116 Running QA tests (pressure or water tightness) 113 200 21 334 117 Preventive maintenance for equipment 35 264 35 334 118 Corrective maintenance for equipment 42 208 84 334 119 Going to/coming back from lunch out of schedule 13 72 249 334 120 Waiting for the concrete bucket to pour concrete 14 90 230 334 121 Transporting an empty bucket 7 112 215 334 122 Waiting 1 76 257 334 123 Redoing work (Straightening steel reinforcement) 4 90 240 334 124 Idle time 2 75 257 334 125 Going to the toilette 1 129 204 334 126 Walking empty handed 4 71 259 334 127 Having breakfast 13 119 202 334 128 Redoing work 17 83 234 334 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 Table 3. Groups of activities result from the survey Item Activity Work Type Code 1 Alignment PW PW 01 2 Application of materials PW PW 02 3 Filling PW PW 03 4 Fusion of water pipes PW PW 04 5 Installation PW PW 05 6 Leveling PW PW 06 7 Placement of materials PW PW 07 8 Placement of formwork PW PW 08 9 Plastering PW PW 09 10 Preparation of material PW PW 10 11 Sand door frame PW PW 11

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 14 of 24 Table 3. Cont Item Activity Work Type Code 12 Vibrating concrete PW PW 12 13 Wiring PW PW 13 14 Applying mold release agent CW CW 01 15 Assembly of scaffold CW CW 02 16 Carrying material or tools CW CW 03 17 Cleaning CW CW 04 18 Construction site inspection CW CW 05 19 Cutting CW CW 06 20 Demarcation of work area CW CW 07 21 Drilling CW CW 08 22 Enable cutting machine CW CW 09 23 Giving instructions CW CW 10 24 Installation of prevention measures CW CW 11 25 Lifting equipment with a crane CW CW 12 26 Maneuvering pipes or accessories to productive work CW CW 13 27 Moving materials CW CW 14 28 Patching wall to install tiles or pipes CW CW 15 29 Placement of equipment CW CW 16 30 Preparing workspace CW CW 17 31 Receiving instructions CW CW 18 32 Removing CW CW 19 33 Safety supervision CW CW 20 34 Shoveling CW CW 21 35 Taking measurements CW CW 22 36 Test CW CW 23 37 Verifying CW CW 24 38 Wet wall for masonry works CW CW 25 39 Having breakfast NCW NCW 01 40 Idle time NCW NCW 02 41 Redoing work NCW NCW 03 42 Standing worker NCW NCW 04 43 Transporting an empty bucket NCW NCW 05 44 Unproductive trip NCW NCW 06 45 Using the restroom NCW NCW 07 46 Waiting NCW NCW 08 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 A 2300, with a 16.0 MP Image Sensor, DIGIC 4 Image Processor, 5 x Optical Zoom, 720 p HD video recording and 16 effective megapixels.

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 15 of 24 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 . Table 4. Initial Level of implementation of the LPS of the Project Last Planner System Element Implementation Rate Master plan 100% Health and safety plan 100% Pull Planning Session 100% Lookahead 100% Percent Plan Completion (PPC) 100% Collaborative Safety Planning 50% 5 Why Analysis and Corrective Measures 25% 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 5. Work Sampling based on the new classification Activity Number Type of Work Type of Act Type of Condition Classification Brick placement 3 PW SA SC PW-SA-SC Brick placement 2 PW SSA SC PW-SSA-SC Filling door frame 4 PW SSA SC PW-SSA-SC Fusing water pipes 2 PW SSA SC PW-SSA-SC Installation of elevator 3 PW SA SC PW-SA-SC Installation of elevator 2 PW SSA SC PW-SSA-SC Installing ceramic tiles 2 PW SSA SC PW-SSA-SC Installing electric pipes 9 PW SA SC PW-SA-SC Installing electric pipes 2 PW SSA SC PW-SSA-SC Installing gas pipes 3 PW SA SC PW-SA-SC Installing hinges on door 2 PW SSA SC PW-SSA-SC Installing horizontal reinforcement 3 PW SA SC PW-SA-SC Installing profiles for drywall 2 PW SSA SC PW-SSA-SC Installing rectangular boxes 3 PW SA SC PW-SA-SC Installing sewage pipes 2 PW SSA SC PW-SSA-SC Installing wallpaper 2 PW SSA SC PW-SSA-SC Installing window frame 3 PW SA SC PW-SA-SC

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 16 of 24 Table 5. Cont Activity Number Type of Work Type of Act Type of Condition Classification Introducing cable guides in electrical pipes 3 PW SA SC PW-SA-SC Introducing cable guides in electrical pipes 6 PW SSA SC PW-SSA-SC Level out concrete 6 PW SA SC PW-SA-SC Level out concrete 3 PW SSA SSC PW-SSA-SSC Level out concrete with a shovel or foot 2 PW SSA SC PW-SSA-SC Placement of wire 18 PW SA SC PW-SA-SC Placement of wire 4 PW SSA SC PW-SSA-SC Placing accessories in wall formwork 6 PW SA SC PW-SA-SC Placing plywood in wall formwork 3 PW SA SC PW-SA-SC Placing telecommunications cable 2 PW SSA SC PW-SSA-SC Plastering drywall 2 PW SSA SC PW-SSA-SC Plastering wall 3 PW SA SC PW-SA-SC Plastering wall 2 PW SSA SC PW-SSA-SC Preparing electric material 2 PW SSA SC PW-SSA-SC Preparing material to install pipes 3 PW SA SC PW-SA-SC Preparing melamine cabinets 2 PW SSA SC PW-SSA-SC Preparing mortar 2 PW SSA SC PW-SSA-SC Sanding door frame 3 PW SA SC PW-SA-SC Sanding door frame 2 PW SSA SC PW-SSA-SC Vibrating concrete 2 PW SSA SC PW-SSA-SC Wall grinding 6 PW SA SC PW-SA-SC Wall grinding 8 PW SSA SC PW-SSA-SC Applying mold release agent 2 CW SA SC CW-SA-SC Carrying tools 2 CW SA SC CW-SA-SC Cleaning 14 CW SA SC CW-SA-SC Drilling on demolition debris 2 CW SA SC CW-SA-SC Drilling on melamine cabinets 2 CW SSA SC CW-SSA-SC Erect scaffolding 2 CW SA SC CW-SA-SC Giving instructions 2 CW SA SC CW-SA-SC Giving instructions 2 CW SSA SC CW-SSA-SC Going to the toilette 2 CW SA SC CW-SA-SC Installing safety rails 2 CW SA SSC CW-SA-SSC Using scaffolding 1 CW SA SSC CW-SA-SSC Laying out 2 CW SA SC CW-SA-SC Measuring 2 CW SA SC CW-SA-SC Measuring 10 CW SSA SC CW-SSA-SC Preparing workspace 2 CW SA SC CW-SA-SC Receiving instructions 4 CW SA SC CW-SA-SC Receiving instructions 2 CW SSA SC CW-SSA-SC Removing accessories in wall formwork 2 CW SA SC CW-SA-SC Removing accessory 2 CW SA SC CW-SA-SC Removing formwork struts 2 CW SA SC CW-SA-SC Removing plywood in wall formwork 3 CW SA SSC CW-SA-SSC Removing plywood in wall formwork 4 CW SA SC CW-SA-SC Removing plywood in wall formwork 6 CW SSA SC CW-SSA-SC Risk Prevention 2 CW SA SC CW-SA-SC Risk prevention—Securing lifeline 2 CW SSA SC CW-SSA-SC Running hydrostatic test 2 CW SSA SC CW-SSA-SC Set up cutting machine 2 CW SSA SC CW-SSA-SC Shoveling 4 CW SA SC CW-SA-SC Transporting material 36 CW SA SC CW-SA-SC Transporting material 8 CW SSA SC CW-SSA-SC Transporting materials with a crane 2 CW SSA SC CW-SSA-SC Transporting objects 8 CW SA SC CW-SA-SC Transporting objects 4 CW SSA SC CW-SSA-SC Verifying before wall grinding 2 CW SA SC CW-SA-SC Verifying the alignment of the ceiling 2 CW SSA SC CW-SSA-SC Water leak test 2 CW SA SC CW-SA-SC Wet wall for masonry works 2 CW SA SC CW-SA-SC Idle time 15 NCW SA SC NCW-SA-SC Idle time 34 NCW SSA SC NCW-SSA-SC Idle time 9 NCW SA SSC NCW-SA-SSC

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 17 of 24 Table 5. Cont Activity Number Type of Work Type of Act Type of Condition Classification Redone work—Drilling on slab 3 NCW SA SSC NCW-SA-SSC Redone work—Drilling on slab 3 NCW SA SC NCW-SA-SC Redone work—Drilling wall 3 NCW SA SC NCW-SA-SC Repairing slab 6 NCW SA SC NCW-SA-SC Standing worker 12 NCW SA SC NCW-SA-SC Standing worker 4 NCW SSA SC NCW-SSA-SC Standing worker 3 NCW SA SSC NCW-SA-SSC Transporting an empty bucket 2 NCW SSA SC NCW-SSA-SC Unproductive trip 9 NCW SA SC NCW-SA-SC Unproductive trip 10 NCW SSA SC NCW-SSA-SC Table 6 shows the summary of this evaluation and four video snapshots and their work classifications Table 6. Application of new classification and video snapshots Code Number Percentage PW-SA-SC 78 19.3% PW-SA-SSC 0 0% PW-SSA-SC 58 14.4% PW-SSA-SSC 3 0.7% CW-SA-SC 102 25.3% CW-SA-SSC 6 1.5% CW-SSA-SC 44 10.9% CW-SSA-SSC 0 0% NCW-SA-SC 48 11.9% NCW-SA-SSC 15 3.7% NCW-SSA-SC 50 12.4% NCW-SSA-SSC 0 0% 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 . Table 7. Work sampling based on the new classification after corrective measures Activity Number Type of Work Type of Act Type of Condition Classification Installing electric pipes 17 PW SA SC PW-SA-SC Installing electric pipes 1 PW SSA SC PW-SSA-SC Installing gas pipes 5 PW SA SC PW-SA-SC Installing gas pipes 6 PW SSA SC PW-SSA-SC Installing reinforcement 15 PW SA SC PW-SA-SC Installing reinforcement 1 PW SSA SC PW-SSA-SC Installing sewage pipeline 2 PW SA SC PW-SA-SC Installing sewage pipeline 3 PW SSA SC PW-SSA-SC Installing water pipes 4 PW SA SC PW-SA-SC Installing water pipes 8 PW SSA SC PW-SSA-SC Level out concrete 1 PW SA SC PW-SA-SC Placement of formwork 34 PW SA SC PW-SA-SC Placement of formwork 1 PW SSA SC PW-SSA-SC Placing separators for concrete 5 PW SA SC PW-SA-SC Placing struts in formwork 9 PW SA SC PW-SA-SC Placing wire 15 PW SA SC PW-SA-SC Placing wire 3 PW SSA SC PW-SSA-SC Pouring concrete 4 PW SA SC PW-SA-SC Preparing material 13 PW SA SC PW-SA-SC Preparing material 2 PW SSA SC PW-SSA-SC Preparing reinforcement 3 PW SA SC PW-SA-SC Vibrating concrete 3 PW SA SC PW-SA-SC Applying mold release agent 1 CW SA SC CW-SA-SC

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 18 of 24 Table 7. Cont Activity Number Type of Work Type of Act Type of Condition Classification Assemble scaffolding 5 CW SA SC CW-SA-SC Cleaning 15 CW SA SC CW-SA-SC Cleaning 4 CW SSA SC CW-SSA-SC Cleaning formwork 1 CW SA SC CW-SA-SC Cleaning reinforcement 2 CW SA SC CW-SA-SC Giving instructions 8 CW SA SC CW-SA-SC Giving instructions 5 CW SSA SC CW-SSA-SC Laying out 3 CW SSA SC CW-SSA-SC Measuring 17 CW SA SC CW-SA-SC Measuring 11 CW SSA SC CW-SSA-SC Posting signs 1 CW SSA SC CW-SSA-SC Transporting formwork 2 CW SA SC CW-SA-SC Transporting formwork 2 CW SSA SC CW-SSA-SC Transporting objects 1 CW SA SC CW-SA-SC Preparing work area to pour concrete 2 CW SA SC CW-SA-SC Receiving instructions 12 CW SA SC CW-SA-SC Receiving instructions 5 CW SSA SC CW-SSA-SC Removing struts 2 CW SA SC CW-SA-SC Transporting material 48 CW SA SC CW-SA-SC Transporting material 4 CW SSA SC CW-SSA-SC Transporting materials with a crane 9 CW SA SC CW-SA-SC Transporting objects 30 CW SA SC CW-SA-SC Transporting scaffolding 2 CW SA SC CW-SA-SC Unloading joists 3 CW SA SC CW-SA-SC Idle time 9 NCW SA SC NCW-SA-SC Idle time 1 NCW SSA SC NCW-SSA-SC Redone work—Drilling 1 NCW SA SC NCW-SA-SC Unproductive trip 4 NCW SA SC NCW-SA-SC Unproductive trip 3 NCW SSA SC NCW-SSA-SC Waiting 26 NCW SA SC NCW-SA-SC Waiting 2 NCW SSA SC NCW-SSA-SC Wall grinding 8 NCW SA SC NCW-SA-SC 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 Table 8. Improvement in production and safety Code Number Percentage PW-SA-SC 130 32.2% PW-SA-SSC 0 0% PW-SSA-SC 25 6.2% PW-SSA-SSC 0 0% CW-SA-SC 160 39.6% CW-SA-SSC 0 0% CW-SSA-SC 35 8.7% CW-SSA-SSC 0 0% NCW-SA-SC 48 11.9% NCW-SA-SSC 0 0% NCW-SSA-SC 6 1.5% NCW-SSA-SSC 0 0% 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

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 19 of 24 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 Tables 6 and 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 Table 9. Percentages of measurements in a year Code Percentage PW-SA-SC 37.16% PW-SA-SSC 0.03% PW-SSA-SC 4.86% PW-SSA-SSC 0.04% CW-SA-SC 32.10% CW-SA-SSC 0.05% CW-SSA-SC 5.34% CW-SSA-SSC 0.06% NCW-SA-SC 17.13% NCW-SA-SSC 0.08% NCW-SSA-SC 3.08% NCW-SSA-SSC 0.07% 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 Table 10. Accident rate of a Peruvian construction company [ 60 ]. Indicator 2017 Number of man hours 16,535,491 Number of workers 3828 Number of restricted work case 17 Number of minor accidents 30 Number of fatal accidents 0 Working days lost due to accidents 450

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 20 of 24 Then, Tables 9 and 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 . Table 11. Hours worked in a year Code Percentage Hours Worked PW-SA-SC 37.16% 6,144,588 PW-SA-SSC 0.03% 4961 PW-SSA-SC 4.86% 803,625 PW-SSA-SSC 0.04% 6614 CW-SA-SC 32.10% 5,307,893 CW-SA-SSC 0.05% 8268 CW-SSA-SC 5.34% 882,995 CW-SSA-SSC 0.06% 9921 NCW-SA-SC 17.13% 2,832,530 NCW-SA-SSC 0.08% 13,228 NCW-SSA-SC 3.08% 509,293 NCW-SSA-SSC 0.07% 11,575 100% 16,535,491 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 Tables 10 and 11 divided by 17 Int. J. Environ. Res. Public Health 2023 , 20 , x 21 of 25 Table 11. Hours worked in a year. Code Percentage Hours Worked PW-SA-SC 37.16% 6,144,588 PW-SA-SSC 0.03% 4961 PW-SSA-SC 4.86% 803,625 PW-SSA-SSC 0.04% 6614 CW-SA-SC 32.10% 5,307,893 CW-SA-SSC 0.05% 8268 CW-SSA-SC 5.34% 882,995 CW-SSA-SSC 0.06% 9921 NCW-SA-SC 17.13% 2,832,530 NCW-SA-SSC 0.08% 13,228 NCW-SSA-SC 3.08% 509,293 NCW-SSA-SSC 0.07% 11,575 100% 16,535,491 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 Tables 10 and 11 divided by 17. Figure 3. Correlation Models similar to the Heinrich model. 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 1,605.20 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 Figure 3. Correlation Models similar to the Heinrich model 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 ana-

Int. J. Environ. Res. Public Health 2023 , 20 , 3412 21 of 24 lyzing 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 Funding: This research was partially funded by the Department of Engineering at the Pontifical Catholic University of Peru and the Direcci ó n de Fomento de la Investigaci ó n 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 Tables 1 – 11 . Acknowledgments: 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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