In the previous in Chapter 1, the overview of this study was explained about and the problem was identified. Then from the overview, the aims of the study are to explore the challenges faced in construction site during night time, to identify the different factors associated with safety during night-time construction. Through the chapter, the elaborations of the topic are clearly described. The clarification of the sub-topic will studies about the night time construction, planning aspect, and the impact of night-time construction operations on safety, quality, environmental factors, and productivity.
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2.2 Overview of Night work
2.2.1 Definition of Night work
According to Derek Simpson (2005), night work is defined as a 7 hour period which includes that between midnight and 5am, usually 11pm to 6am. Anyone who normally works at least 3 hours of their working day during this night period is classed as a night worker. Night workers should not work more than an average of 8 hours in every 24. Where such work involves any “special hazards or heavy physical or mental strain” the 8 hours limit applies to each 24 hour period, not an average 8 hours over the reference period.
According to the North Region Construction Night Work Guide (2007), night work is the most difficult and challenging time for the contractor to work to meet his contractual obligations and therefore the most difficult time for the inspector to ensure the work meets the standards and levels of quality while also ensuring that everything is done safely.
2.2.2 Safety Management Plan for Night time Work
A management plan should be well documented and structured so that both employers and employees can benefits from its use. The following are recommended components of a safety management plan for night time works(:
Site personnel responsibility
It should be determined and stated clearly in the safety management plan the responsibility of each individual at construction site for night time works. Project Manager, Engineers, Designers, Safety Officer and Site Supervisors as well as workers each have their specific responsibility to make sure the highest level of priority are given towards safety and health issues.
Permission to work at night
Permission to work at night should be obtained from the relevant authority before construction works at night is carried out. Employers should submit their application for work permit to Local Government Authority and it is advisable to follow all requirements enforced by the authority prior to executing night time construction works. It is also recommended to notify the nearest police station, BOMBA, hospitals or clinics so that they can prepare accordingly in case of an emergency. It is also recommended that night work approved by the local authorities be informed to the residents/occupants of the surrounding neighbourhood.
Inventory preparation for safety equipments
Before night works are carried out, check the inventory of safety equipment to make sure they are sufficiently available, appropriate, and in good working condition. Purchase sufficient new safety equipment for a new construction project or to add existing inventory. Equipments such as retro-reflective signage, barriers, retro reflective tapes and lighting equipment are some example of safety equipment that should be provided for night time construction works.
Material and Machine movement / coordination
Employers should be aware that material and machine movement that is not well supervised could potentially cause serious injury and harm to workers and properties.
Housekeeping
Accidents can occur as a result of poor housekeeping. Hazards at construction site are the same for both day and night shift while the risks of injury are much higher during night works because of the inherent poor illumination. It is essential that the workplace is kept clean and tidy to ensure safety and prevent accidents.
Emergency Preparedness and Response (EPR)
One of the most important elements to consider before work at night is carried out is the EPR specifically for night time environment. A well established EPR can help both employer and employees to prepare; response and recover should a disaster occurs.
Public safety
When construction works involves public area, it is important to make sure the safety of the public. Consider the following when planning for night time work; identify the hazards for example construction vehicle movement or too much glare from lighting equipment and plan for vehicular movement to not interrupt peak hours and make sure adequate supervision is provided for such movement.
Provide sufficient signage to warn the public and put barriers at a safe distance to keep the public away.
Set up a safe walk ways where it is unavoidable to work near or in public vicinity.
Arrange noisy equipments or machinery at farthest point from the public or adopt an engineering control to reduce the noise.
When overhead crane is operating near the public, clear off the area and make sure adequate supervision is in place.
Schedule for daily cleaning of the adjacent public road and filling up holes as well as uneven surfaces.
Working hours & manpower arrangement
Employers should identify at which construction phase the need for night time work is required. Consider the following when planning for night time work; arrange a special team to work at night and allow for shift rotation and inform workers of the “special” hazards and risks at night to allow effective adaptation with the work environment.
It is also recommended to send workers for health screening to make sure the workers are fit to work at night. Allowing an unfit worker to work at night will endanger the worker and other worker in the same work area.
2.3 Overview of Night-time construction
According to the Guidelines for Construction Activities at Night (1999), there is an increasing demand for performing construction of highways and buildings at night, especially in the urban areas to reduce conflict between the public and the stakeholders of the projects. This approach can be beneficial in particular, for reducing traffic disruptions and meeting the completion deadlines. However, contractors should consider the increased safety risk at the workplace when conducting any construction activities at night.
2.3.1 Planning of construction work at night
Working during night time by its very nature is dangerous. Workers are exposed to many high risk unsafe working conditions at construction site. Common problems that might occur are poor visibility in the working environment, working in a drowsy condition, and communication problems with the day shift. This could contribute to other work related safety and health problems for example drug and alcohol abuse, psychological problems, and physiological problems. (Shane J.S., 2012).
Therefore, it is very important to plan any works for night time is engaged. Employers need to plan before hand the workforce required, special arrangement for safety provision such as sufficient work area lighting, retro-reflective clothing, flashing lights on equipments or structures and retro-reflective tape at work area surroundings.
2.3.2 Factors affecting night time work
In order to decide when to conduct night time work, factors (parameters) affecting night time work must be identified. The following factors were identified: (Douglas K.D., 2003)
Risk
Illumination
Nuisances
Productivity
Cost
Safety
Risk
Night time construction introduces numerous risks to a construction project. One clear set of examples is driver and worker fatigue and reduced visibility, which are factors that could increase safety risks. Other major factors contributing to the risks of night time work are human factors such as sleep, stress, work, social or domestic issues, and psychological characteristics, such as appetite and safety. Additional factors associated with the risks of night time construction work zones are reduced work space for machinery and equipment movement, inadequate lighting, high speed of traffic during the night, and long working hours (12 to 14 hours). (Shane J.S., 2012).
Risk management process
The best way to address night time construction work-zone risks and hazards is through risk management programs. It is suggested that agencies and contractors begin their risk management processes early and review the risk management program carefully prior to beginning night time work. Risk management is the term used to describe a sequence of analysis and management activities focused on identifying and creating a response to risks and, in the case of night time construction, to project-specific risks (Shane J.S., 2012). Various organizations use very similar steps, but slightly different terms, to describe their risk management approach. These are the important risk management steps:
1. Risk identification.
2. Risk assessment/analysis.
3. Risk mitigation and planning.
4. Risk allocation.
5. Risk monitoring and control.
Risk identification is the process of determining which risks might affect the project and documenting their characteristics using tools such as brainstorming and checklists.
Risk assessment/analysis involves the quantitative or qualitative analysis that assesses impact and probability of risk.
Risk mitigation and planning involves analyzing risk response options (acceptance, avoidance, mitigation, or transference) and deciding how to approach and plan risk management activities.
Risk allocation involves placing responsibility for a risk on a specific party or parties typically through a contract. The fundamental tenets of risk allocation include allocating risks to the party that is best able to manage them, allocating risks in alignment with project goals, and allocating risks to promote team alignment with customer-oriented performance goals.
Risk monitoring and control is the capture, analysis, and reporting of project performance, usually as compared to the risk management plan. Risk monitoring and control assists in tracking and resolution.
Types of Risk
The first step in an effective risk management program is to identify possible risks. Specific concerns related to night time work zones include poor visibility and work quality, staffing issues, unwanted noise and glare, decreased worker and driver alertness, impaired drivers, higher vehicle speeds, increased labour costs, materials and traffic control, and problems in logistics and supervision. These risks are categorized broadly as safety, cost/production and schedule, quality, organizational relationships, technical, construction, economic, and environmental.
Illumination
Night time construction lighting arrangements have an impact on project safety, quality, cost, and productivity. One of the main reasons illumination levels have a strong impact on the other aspects of night time construction is the fact that light influences human performance and alertness.
Recommended lighting level
A major problem with night time work-zone lighting arrangements is the insufficiency of the lighting provided to perform the construction or maintenance task. The level of lighting needed for specific construction activities depends on factors related to the humans performing the activities, as well as factors relating to the task at hand and the environment in which it takes place.
For example, visual ability is a human factor that is known to vary among workers. Therefore, lighting standards assume reasonable visual abilities that are considered to be normal, while giving some allowance for variations among individuals. This assumption allows for visual standards to be based mainly on the visual requirements of the specific tasks construction activities required (Shane J.S., 2012).
Task Dependency
Visual Standard
Required Accuracy
The higher the precision required in a task, the higher the level of illumination needed.
Background Reflection
The ability to visualize an object or a target depends on the contrast between that object and the background. Highly reflective backgrounds decrease the visibility of the target or object.
Relative Speed
The relative speed of the object/target or its observer is another factor directly affecting the level of lighting needed for the construction task.
Faster moving objects or targets necessitate higher levels of illumination.
Objective Speed
The size of the target observed in construction tasks has an impact on the needed level of illumination for the task. The smaller the object, the higher the level of lighting needed.
Seeing distance
The distance between the observer and the target in each task is another determining factor in setting illumination levels. Larger distances necessitate higher levels of illumination.
Table 2.1: Task-dependent visual standards
Sources: A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity.
Nuisances
Sound
Sound is energy in motion as a pressure wave through the air produced by a vibrating body. A decibel (dB) is the basic sound level unit; it denotes a ratio of intensity to a reference sound. Most sounds that humans are capable of hearing have a decibel range of 0 to 140. Zero dB, by international agreement, corresponds to an air pressure level of 20 micro-Pascals (in other words, the agreed-upon threshold of hearing). A whisper is about 30 dB, conversational speech is about 60 dB, and 130 dB is the threshold of physical pain. Humans sense the intensity difference of one sound from another. A three-decibel change in noise level is a barely noticeable difference, while a 10-dB change is perceived subjectively as a doubling/halving in loudness (Shane J.S., 2012).
Noise
Noise can seriously harm human health and interfere with people’s daily activities at school, at work, at home and during leisure time. According to World Health Organization (WHO) (2004), the main health risks of noise identified are:
Pain and hearing fatigue
Hearing impairment including tinnitus
Annoyance
Interferences with social behaviour (aggressiveness, protest and helplessness)
Interference with speech communication
Sleep disturbance and all its consequences on a long and short term basis
Cardiovascular effects
Hormonal responses (stress hormones) and their possible consequences on human metabolism (nutrition) and immune system
Performance at work and school
Environment
Critical health effect
Sound level dB(A)*
Time hours
Outdoor living areas
Annoyance
50-55
16
Indoor dwellings
Speech intelligibility
35
16
Bedrooms
Sleep disturbance
30
8
School classrooms
Disturbance of communication
35
During class
Industrial, commercial and traffic areas
Hearing impairment
70
24
Music through earphones
Hearing impairment
85
1
Ceremonies and entertainment
Hearing impairment
100
4
Table 2.2: WHO Community Noise Guidance
Sources: Occupational Noise-World Health Organization
Vibration
According to Shreve (1994), vibration can be defined as simply the cyclic or oscillating motion of a machine or machine component from its position of rest.
Many types of construction activities cause vibrations that spread through the ground (ground-borne), most notably pile driving, hoe ram demolition, blasting, and vibratory compacting. Though the vibrations diminish in strength with distance from the source, they can produce annoying or objectionable audible and “feel able” levels in buildings very close to construction sites.
Rarely do vibrations reach levels that cause structural damage to buildings. However, minor cosmetic damages can occur at lower vibration levels and, in the case of old, fragile, or historical buildings, a danger of significant structural damage always exists.
Dust
During the night, many households leave their windows open to take advantage of the cool night air. With urban night time construction projects being very close to people’s living space, dust can be a problem.
Night time construction dust problems are accentuated by the lighting, which makes the particulate matter very visible. Fugitive dust may be generated by construction operations, and the contract specifications should require that the contractor prepare a dust control plan. In many cases, dust control is not a problem that is limited to night time activities; therefore, air quality or dust control plans should be for all hours of the day or night (Shane J.S., 2012).
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