Tuesday, 24 November 2009

The Unsafe Acts and the Decision-to-Err Factors of Thai Construction Workers

*Thanet Aksorn and B.H.W. Hadikusumo


In Thailand, many construction activities have been carried out to meet the high demands of the expansive market. However, the construction industry has faced a wide range of challenges, one of which is the high accident and injury rate at the project level. According to the accident rate in all industries recorded by Ministry of Labour (International Labour Organization, 2005), the rate of accidents and fatalities in Thai construction is reported as the highest. In 2003, the construction industry accounts for 14% of the total number of 787 deaths at work and 24% of the total 17 cases of permanent disability. Construction is a labor intensive industry, in which workers play a very important role in the success of the various projects undertaken. Thus, the need to protect workers from accidents becomes a major consideration in any construction organization. For many years, safety practitioners have addressed physical preventive measures such as machine guarding, housekeeping and inspection, since poor physical conditions are believed to cause accidents. However, not much preventive work has been done on the human aspects. The fact that many researchers are of the opinion that unsafe acts of workers are the major contributors of accidents and injuries, rather than poor working conditions (e.g., Sawacha et al., 1999; Abdelhamid and Everett, 2000; Stranks, 2000; Haupt, 2001; Holt, 2001; Goetsch, 2005), suggests that there is the need for a change of direction in construction safety research to identify the possible influential factors of workers' decisions.

Theoretically, there are two types of unsafe acts, which can be classified as either errors or violations (Reason, 1990). In the most accident databases, the errors are major contributor to accidents. Violations, on the other hand, are less common. Unsafe acts of workers may occur in two conditions. First, a worker does not know while he/she is acting unsafely and second, he/she knows while he/she is acting unsafely. The first case can be easily tackled by providing safety education to the worker, close supervision, good work system design, etc. However, the second case is more complex because the reasons for acting unsafely could be due to different factors, such as the worker's personality, the nature of the job being undertaken, the extent of managerial support and workgroup influence. The second case is known as "the worker's decision-to-err", in which, though a worker is fully aware that he/she is working unsafely, he/she still decides to carry on with such unsafe acts. Therefore, knowing the causes behind the decisions to act unsafely can enable construction projects to develop the appropriate strategies to improve working practices of workers. This is the purpose for which this research was conducted.


This research is designed to investigate the relationship between the decision-to-err factors and the unsafe acts. This relationship is important for management to study what unsafe acts could occur on the site, to find out what decision-to-err factors might contribute to these unsafe acts and to develop solutions which could reduce such unsafe acts.


Generally, accidents at work occur either due to unsafe working conditions and unsafe worker acts. In construction, it is suggested that unsafe act is the most significant factor in the cause of site accident (Sawacha et al., 1999; Abdelhamid and Everett, 2000). There is no general agreement on definition of an unsafe act. However, it has been defined in similar focus on unaccepted practices which have the potential for producing future accidents and injuries. For example, Stranks (2000) gave the definition of unsafe act as "…any act that deviates from generally recognized safe way of doing a job and increases the likelihood of an accident…". Several unsafe acts have been identified by many researchers such as Petersen (1984), Anton (1989), Stranks (1994), Simachokdee (1994), Michuad (1995), Abdelhamid and Everett (2000), and Holt (2001).

These unsafe acts are:

• Working without authority on the job can cause accidents since unauthorized workers may lack the necessary skills, or unfamiliar with the job process.

• Failure to warn or to secure members out of danger is considered as an unsafe act since many accidents occur because workers pay less attention to warning or securing co-workers who are working under conditions with high probability of accident occurrence.

• Working at improper speeds, exceeding the prescribed speed limits, or unsafe speed actions could cause accidents, e.g. workers who handle objects quickly could slip and be injured.

• Improper lifting, handling, or moving of objects may cause serious back pains, e.g. workers who manually lift heavy objects without proper force-saving equipment.

• Improper placing and stacking of objects and materials in dangerous locations can result in unpredicted accidents e.g. a worker could collide with such objects.

• Incorrect use of tools and equipment, hand tools, power tools, and machinery can also cause accidents. For instance, workers who frequently climb or stand on rebars instead of using a ladder could fall down.

• Using defective equipment and tools to work, e.g. a worker who uses a substandard ladder could fall and be injured.

• Annoyance and horseplay in the workplace such as young workers who play roughly around the workplace could encounter unexpected accidents.

• Ignoring to wear personal protective equipment (PPE) may increase chances of getting injured, e.g. workers without hardhats are more prone to getting head injuries from falling objects.

• Removing safety guards from the workplace or equipment could raise the chances of getting accidents, e.g. workers who remove guardrails could fall down.

• Smoking, creating naked flame or sparks in areas where flammable materials are stored could cause explosions.

• Leaving nails or other sharp objects protruding from timber may cause accidents as workers who do not wear safety shoes could step on these objects and be injured.

• Throwing or accidentally dropping objects from high levels could expose other workers to sustaining possible head injury.

• Working under the effects of alcohol and other drugs could increase workers' unawareness and cause serious accidents.

• Improper positioning of tasks can also result in accidents, e.g., workers on high levels could fall and be seriously injured.

• Improper posture for tasks such as workers taking shortcuts by climbing or jumping from high levels instead of using ladders could result in serious injury.

• Servicing equipment which is in operation, e.g. refueling a machine without first turning off the engine could cause a severe accident.

• Working with lack of concentration, such as workers talking while undertaking a job could cause distraction and result in an accident.

• Working in poor physical conditions such fatigue, stress, or drowsiness could also increase the likelihood of accidents.


The decision-to-err can contribute to human errors which could subsequently lead to the occurrence of accidents (Wiegmann et al., 2005). On the other hand, human errors could stem from the decisions made by workers (LaDou, 1994). For instance, if a supervisor pressures a worker to increase the rate of production, the worker might choose an unsafe approach rather than a safe one in order to save time and get the job done as quickly as possible. Petersen (1984) proposed a causation model which explains that the decisions of workers to err are due to three main causes:

1. Logical decisions in different situations such as peer pressure, close supervision, management priorities, and personal value system.

2. Unconscious decisions-to-err, which includes proneness and mental problems.

3. Perceived low probability in which the workers believe that they will not have an accident.

Decision-to-err factors were gathered from literature review and interview with 20 Thai construction workers. Twenty factors were identified and grouped under four categories: personal, job, management and workgroup.



Hall (1995) stated that most workers prefer to take shortcuts to save time because they want to avoid supportive activities. Workers oftentimes prefer to work with the wrong tools because they feel that it is too much trouble getting the right one, e.g. workers could climb or stand on rebars (an inadequate working platform) instead of using a proper ladder.

Past Experience

Some workers, having performed a job in a familiar way for many years are very reluctant to give up their old way of doing things. However, these old habits could prevent them from noticing the prevailing hazards, thereby increasing the possibility of accidents occurrence (Kittleson, 1995).

Being in a Hurry

Stice (1995) stated that pressure from supervisors to get jobs done quickly can cause the workers to work in hurry. As a result of such pressures, workers may disregard good safety practices to save time for completing the jobs.

Showing Off

"Watch me" is usually heard from workers who like to display their manhood in order to gain the admiration of their colleagues. Kittleson (1995) stated that some "macho" types of workers like to show off their capability to their peer improperly. This "show-off" behavior can, and often does, results in accidents.

Being Angry

Kittleson (1995) mentioned that being angry can lead to accidents because anger nearly always rules over caution. When someone gets angry, he or she will start to sweat, tremble, get knots in the stomach, or grind his/her teeth. Unresolved anger could cause distraction, proneness to accidents, anxiety, violence and rage.

Being Uncomfortable

The International Labour Organization (ILO, undated) revealed that PPE can be uncomfortable, can decrease work performance and can create new health and safety hazards. Some workers for instance, reject the wearing of earmuff because it makes them feel hot, especially when it is used in hot regions.

Effects of Using Drugs and Alcohol

Michuad (1995) stated that workers who use drugs and alcohol have the tendency to distort or block their decision-making capability. In general, experimental research has shown that alcohol has a delirious effect on performance due to its effects on judgment, reasoning and memory. Drugs users and drinkers often experience reduced levels unawareness, a situation which could lead to decision errors and unsafe working. When the influence of the drug or alcohol is over, a worker might wonder why he did the unsafe act.

Supervisor's and Co-workers' Acceptance

In order to gain the acceptance of supervisors or coworkers, a worker could choose to perform a job unsafely. For example, a worker could decide to unload some materials faster so as to save time for completing the job and thereby gain the acceptance, approval or the admiration of his/her supervisor or co-workers.


Confidence is a good thing, but overconfidence would oftentimes do more harm than good. "It will never happen to me" attitude could lead to improper procedures or methods that could cause injury (Hirsch, 1998).


Stress has been defined as human's reaction against a threatening situation (Goetsch, 2005). Schermerhorn (2001) further defined stress as "the state of tension experienced by individuals who are facing extraordinary demands, constraints, or opportunities." Some potential factors that could contribute to job stress in the construction industry are:

Too Much Work (Work Overload)

Asking workers to do more than they could handle may result in the workers developing high stress, especially when deadline pressures are put on them. According to Greenberg and Baron (2000), there are two different forms of work overload: quantitative overload, which occurs when individuals are asked to do more and qualitative overload, which refers to employees' belief that they lack of the required skills or abilities to perform the work.

Too Little Work (Work Underload)

Similarly, being asked to do too little could also be as stressful as being asked to do too much. Greenberg and Baron (2000) proposed that there are two types of work underload: quantitative underload, which refers to the boredom arising from having too little work to do, and qualitative underload, which is the lack of mental stimulation, such as routines, and repetitive jobs.

Time Pressure

When workers are unable to meet deadlines, they instantly get overwhelmed and begin to worry (Timm and Peterson, 1986; Stranks, 2000). In addition, when the work process is changed and the workers are not given enough time to complete the job, they easily become stressed.


Management Pressure

Stranks (1994) stated that supervisors who are in charge of low-producing units normally tend to spend more time with their subordinates. These supervisors usually divide job times into many short periods to give specific instructions such as, "do this", "do that", or "do it this way", to their subordinates, hoping to increase productivity. However, supervisors' pressure may cause subordinates to work unsafely while trying to satisfy the supervisors' objectives, such as completing the work within unreasonable time schedule.

Management Support

Hammer and Price (2001) proposed that in order to ensure construction site safety, management should fully support and ensure that safety devices and temporary structures are in good conditions, allocate sufficient budgets for establishing safe works, and establish an effective program to monitor and audit operational activities for their safety.


LaDou (1994) stated that it is very obvious that any successful safety program must necessary involve the supervisors. Supervisors should closely control all the workers activities. If supervisors could convince workers that safety has to be considered all the time, then the workers will do everything to prevent accidents.

Reward and Penalty

Motivational factors from the management could have negative impact on inspiring workers to work safely as inappropriate ways of giving rewards and penalties could motivate workers to work unsafely. For example, a worker may decide to work unsafely because he/she thinks that doing this can speed up the work, which would mean getting more reward such as bonus. Penalty could also motivate workers to work unsafely, e.g. a worker who is physically unfit could force himself/herself to go to work, out of the fear of being penalized.


Group Norms

Each employee is not just an individual, but a member of a group as well (Stranks, 1994; Gibson et al., 2000). Each group has its own norms, sets its own work goals, moral standards, and makes its own decisions. The norms also incorporate the behavior of workers towards their boss, and how workers react towards safety regulations. Kittleson (1995) stated that it is easier for the workers to base their behavior on others than to do the right thing. For example, a worker may hear, "everyone else does it that way" and therefore follow the group in working in a similar way even though it is an unsafe method.

Group Pressure

Ellis and Fisher (1994) stated that certain groups pressure their members to conform to their established norms, otherwise, erring members will be penalized.


The unsafe acts practices and the decision-to-err factors influencing workers' unsafe acts on construction sites in Thailand were explored in this study. Nevertheless, there are some limitations of the study need to be elucidated. It should be noted that the ranking of frequencies of unsafe acts was obtained from the workers' recall. The frequencies did not come from actual field observation; therefore, the ranking does not necessarily correspond to the current situation of unsafe acts. Additionally, a number of unsafe acts were limited to the workers since a list already provided by the authors. The results revealed that the most frequent unsafe acts committed by construction workers are: (1) the workers rarely wear PPE while doing their jobs; (2) the workers lift or handle objects or materials improperly; and (3) the workers leave nails and other sharp objects in dangerous locations.

Our study also indicated that there are some relationships between the workers' characteristics (i.e., age, occupation and experience) and the unsafe acts. The four subgroups of workers classified by age are different in making annoyance and horseplay in the workplace. The young workers tend to commit this unsafe act more often than the older group. The four subgroups of workers classified by their experience differ in wearing PPE, leaving nails or sharp objects in dangerous locations, and working in dangerous positions. Inexperienced workers tend to ignore wearing PPE, and work in dangerous positions rather than the experienced ones, whereas, experienced workers tend to be more frequent in leaving nails or other sharp objects in dangerous locations. Moreover, the five subgroups of workers classified by their job occupation are different in seven types of unsafe acts. The results indicated that carpenters are more often in working without authority and skills, and in leaving nails or sharp objects in dangerous locations. Masons tend to be more in improper lifting, handling and moving materials, and in throwing and dropping materials from high levels compared to others.
Furthermore, steel workers tend to be more in making annoyance and horseplay, and removing safety guards; while, unskilled workers tend to be more in ignoring to wear PPE at the workplace.

In order to explain why the unsafe acts happen, the decision-to-err factors were also explored. It was determined that there are many potential decision-to-err factors causing unsafe acts, the stepwise multiple regression analysis was then employed to remove insignificant factors. The most frequent unsafe acts rated by more than 30 respondents were selected. The minimum of 30 respondents is the requirement for parametric test of statistical analysis. The first unsafe act, rated by 140 workers, was the failure to wear PPE. This unsafe act was statistically correlated with five factors: lack of management support, group norms, overconfidence, being uncomfortable, and past experience. The second unsafe act, rated by 58 workers, was improper lifting, handling and moving objects. This unsafe act was statistically associated with three main factors: group norms, overconfidence, and management pressure. The third unsafe act, rated by 34 workers, was leaving nails or other sharp objects in dangerous locations. This unsafe act was statistically associated with three main factors: group norms, laziness and overconfidence.


This study could be broadened to include a larger workforce sample to enhance the level of reliability of the research. This study can be more complete if the limitations of the study are overcome. It is suggested that the frequency of unsafe acts should be obtained from field observation. The results of observation will be most likely to represent actual state of unsafe acts that occur on sites. As a result of time constraint, this study could not obtain decision-to-err factors for all identified unsafe acts. If it is possible, more research should be carried out to investigate decision-to-err factors for all types of unsafe acts. As a result, managers can develop appropriate preventive measures to reduce the occurrences of those unsafe acts. Finally, it may be of interest to perform a boarder study to investigate the relationships between the occurrences of unsafe acts and site safety performance (e.g., accident rate). By doing this, the managers will know which types of unsafe practices have greater impact on safety performance.

This study was published in the “Journal of Construction in Developing Countries, Vol. 12, No. 1, 2007”. Full journal article is available upon request.

Abstract: The unsafe acts of workers are considered as major contributors of work-related accidents and injuries on construction sites. However, not much work has been done to address the reasons why unsafe acts of workers occur particularly in construction industry. The aim of this paper therefore, is to investigate the major unsafe acts (i.e., at-risk behavior), and the decision-to-err factors causing unsafe acts. A questionnaire survey was conducted to collect data from a total of 214 workers from 20 building construction projects in Thailand. The findings revealed that the failure of workers to wear personal protective equipment (PPE), improper lifting or handling of materials, and keeping sharp objects in dangerous locations, are the major unsafe acts which frequently occur on construction sites in Thailand. In addition, the paper reported that the top three most frequent unsafe acts are statistically associated with several decision-to-err factors, including lack of management support, management pressure, group norms, overconfidence, being uncomfortable, past experience and laziness.

Keywords: Accident, Construction, Decision-to-err, Human factor, Safety, Unsafe behavior.

Construction Engineering and Infrastructure Management, School of Civil
Engineering, Asian Institute of Technology, Pathumthani, THAILAND.
*Corresponding author: artty_th@yahoo.com