A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity (2012)

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48 The productivity of construction operations has many definitions that range from how effec- tive and safe workers are on the job to exact metrics of how many units of a construction product are accomplished in a certain span of time. The definition that is most widely acceptable is the one that focuses on units produced over a defined time duration, or focuses, conversely, on the labor hours needed to produce a unit. Perceptions vary concerning the degree that construction productivity is impacted by work- ing at night. Some judge worker performance as a key factor that can cause decreased nighttime productivity. Other studies cite less traffic congestion as a major contributor to productivity improvement during nighttime shifts. Strong evidence from research studies shows that produc- tivity for many activities is not impacted by nighttime construction operations. Key Take-Away Opinions are contradictory as to whether construction productivity is affected by working at night. Contrary to intuitive beliefs, productivity during nighttime operations may not be affected. This can be attributed to two factors counteracting yet balancing each other. While an expected loss in worker productivity at night might be expected, in many cases, improved work conditions have been found during nighttime hours. STAs need to be sure to consider productivity and production rates, similar to contractors, when developing project phasing and estimating project time and cost. Productivity Study Findings Numerous studies have found no difference in nighttime versus daytime production rates. Studies by Ellis et al. (1993), Dunston et al. (2000), and Colbert (2003) on pavement milling and asphalt paving recorded no difference between day and night shifts in productivity rates. The Ellis et al. (1993) study also reported that the work costs less when conducted at night. Douglas and Park’s (2003) study using 124 datasets from asphalt paving projects found 23 per- cent more tonnage placed per hour at night than during the day. Lee’s (1969) study on concrete paving reported a productivity increase of 1.5 lane-miles per night. Higher productivity levels are attributed to longer working hours and less interference of traffic at night (Elrahman 2008). Key Take-Away The NYSDOT in 2008 found no difference in productivity levels between night and daytime operations. Higher productivity levels at night may be experienced, though, because of less interference from traffic and longer working hours (Elrahman 2008). C H A P T E R 5 Productivity

Productivity 49 Factors Impacting Nighttime Productivity Factors that have a potential impact on nighttime productivity can be grouped into two main classes: human and work environment. Human factors deal with the impact that nighttime work has on construction laborers and supervisors, and work environment deals with issues such as nighttime traffic, availability of support services, and weather impacts. Specific conditions under each class may have either a positive or negative impact on nighttime work productivity. Human Factors Transportation projects have work schedules that require employees to be on site for extended periods of time, frequently during evenings and nights, as well as on weekends. The nature of the work affects worker fatigue through three main pathways: number of hours at work, timing of shift schedule, and task-specific demands of the work (McCallum et al. 2010). Duration and timing of work operations can affect fatigue and loss of productivity primar- ily through sleep loss, which can result from curtailed opportunity for sleep under some work schedules. The third pathway is related to task-specific effects. While extensive scientific litera- ture exists exploring the relationship between fatigue and adverse outcomes in occupational and transportation settings, most occupational work studies have not looked specifically at worker productivity. Most work studies have instead examined work schedule as a precondi- tion for fatigue and tried to quantify a relationship to adverse outcomes such as error, injury, and death. A limited number of studies have evaluated the impact of extended overtime and shift work on labor productivity. These studies have shown that productivity decreases as the number of working hours per week increases. Hanna et al. (2005) focused on labor-intensive activities such as electrical and mechanical work. Overtime in this study was considered to be any work per- formed in addition to the typical 40 hours scheduled per week. Key Take-Away Extended periods of overtime have a long-term impact on labor productivity. The effect on productivity is also dependent on whether the night work is a constant work-shift assignment, meaning that laborers are always assigned to work at night, or a periodic alternation between shifts based on job requirements or rotating day/night shifts. These two dissimilar situ- ations have different impacts on sleep recovery opportunity and circadian rhythm adaptation affecting work productivity (Daan et al. 1984). The circadian process is a 24-hour rhythm produced by the human biological clock. It pro- motes wakefulness during the day and sleepiness during the night, making staying awake through the night a challenge even when managing to get enough sleep beforehand. Fatigue is regulated by the circadian process as a function of time of day. Moreover, the cir- cadian process makes it difficult to get enough sleep during the day, especially during the “wake maintenance zone” in the early evening (Dijk and Czeisler 1994). Circadian patterns have a number of physiological symptoms that affect human performance. As such, fatigue and performance in the workplace is a function of both time awake (due to hours of work) and time of day (due to the work shift) (Åkerstedt 2007), plus the nature of the work. Therefore, circadian patterns of human performance may influence nighttime construc- tion activities in terms of labor productivity (Goel et al. 2011). Most of the data on circadian effects were obtained in laboratory settings where it is possible to control sleep time and measure performance precisely. In controlled settings, it is clear that

50 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity sleep deprivation results in dose-response relationships, with greater sleep deprivation leading to larger performance decrements, and that these effects are cumulative, so that the longer a subject is sleep-deprived, the greater the effect (Van Dongen et al. 2003). However, the relation- ship of laboratory findings to operational settings, while indicative of how sleep has an impact on performance, is far from being direct. One study that evaluated the impact of circadian patterns asked subjects to perform a range of tasks every 2 hours to estimate the magnitude of the endogenous and exogenous components of the subject’s circadian pattern. Performance during the different phases of the circadian cycle was found to be considerably different with respect to the different tasks performed (Folkard et al. 1993). The results indicate that performance of tasks may adjust at varying rates, which means that shift timing and operations need to be adjusted according to the type of work task. Key Take-Away The circadian process is a 24-hour rhythm produced by the human biological clock. It pro- motes wakefulness during the day and sleepiness during the night, making staying awake through the night a challenge even if the worker manages to get enough sleep beforehand. Circadian cycles have an impact on human physical and mental performance. Key Take-Away Circadian patterns have different impacts on physically active versus inactive people. Physi- cally active people (like construction workers) exhibit troughs in their performance during the early morning but have twice the performance of physically-inactive people. People who prefer working at night have improved performance on tasks as the evening progresses, while morning- preferring people have declining performance when working in the evening. Tip Workers should be allowed flexibility in choosing their work shift. Night-preferring workers should perform better at night, while morning-preferring people will perform better during the day. Using a monetary incentive may cause workers to change their preference but not necessarily change their performance. Early mornings should be reserved for less-intense work due to the decreased performance of physically active workers during this period. The general trend in sleep research suggests the best way to address the problem of fatigue and performance in operational settings is with an integrated approach. This is because no single measure or intervention is likely to be particularly effective. Improved performance requires a combination of the following (Rosekind et al. 2006 and Caldwell et al. 2008): • Work hour controls. • Training and education. • Scheduled risk assessment. • Healthy sleep and fatigue countermeasures. Caldwell et al. (2008) delineated the principal strategies for managing alertness in operational contexts. The first element, and arguably the most important, is that management and staff understand the nature of fatigue. The tendency has been to think of fatigue simply as a state of mind that can be overcome with “professionalism” or “endurance.” Such philosophies lead to undesirable results in terms of productivity and safety. Therefore, establishing an understanding about the physiological basis of fatigue, how it man- ifests in work situations, and what can be done about it, are the key components of a training and education program to improve nighttime productivity and safety. A variety of materials are

Productivity 51 available to create programs, such as the Fatigue Management Reference, developed by the U.S. DOT Human Factors Coordinating Committee (McCallum et al. 2003). Resource Commercial Transportation Operator Fatigue Management Reference: http://www.fra.dot.gov/ downloads/research/fatigue_management.pdf Tip The hours of least alertness are between 1 a.m. and 6 a.m. (Moore-Ede et al. 1989). Therefore, in the design of nighttime operations, tasks requiring high levels of skill and alertness should be avoided during these hours. If skill-intensive tasks are to be performed during these hours, special attention should be given to quality control to avoid productivity disruptions caused by rework. The Caldwell et al. (2008) report also provides strategies for improving work/rest scheduling, techniques for optimizing sleep, and techniques for temporarily mitigating fatigue (counter- measures). Work-Zone Factors Work-zone factors affecting productivity include lighting and visibility, traffic controls, and roadway and traffic conditions. If the work zone is dimly lit and quiet, productivity will prob- ably suffer. These factors are discussed in detail in Chapter 3, Illumination, and Chapter 8, Safety. Light exposure affects the timing of the circadian process. Brighter light is more effective at shifting the circadian rhythm, but the timing of light exposure is also critical in determining the degree of shifting and even the direction of shifting (Duffy and Czeisler 2009). Exposure to light in the late evening delays circadian rhythms. Consequently, lighting for nighttime work is necessary both for visibility, to perform the actual work, and in terms of the workforce’s ability to resist fatigue and remain productive. Tip Planned light exposure patterns are helpful in managing the circadian process and mitigating fatigue (Lee et al. 2006). Work Management Countermeasures Work management fatigue countermeasures can decrease the risk of adverse productivity outcomes. Measures to maintain productivity require close management attention to the work environment and tasks. Key Take-Away Of primary importance is the ability of the workforce to gain adequate sleep; therefore, work schedules should provide a minimum of 10 hours off between shifts. Tip Project-site interventions that can be used include the following: • Caffeine. • Naps (Miro et al. 2003). (Tip continued next page)

52 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity • Physical activity to improve physiological alertness (Atkinson et al. 1993). • Breaks to reduce cognitive, time-on-task fatigue (Moore-Ede et al. 1989). Management should institute safety training about fatigue, design work schedules to pro- vide adequate rest for workers, and make work-zone improvements that decrease worker fatigue or anticipate likely fatigue problems (e.g., stepping into traffic and encounters with heavy equipment). In planning nighttime work activities, management needs to think in terms of the physical and cognitive demands of work tasks. This can be a paradigm shift in how work is accomplished and breaks are scheduled. Tip A good practice is to have personnel move around or change tasks during a night shift. While standard practice is to design work zones primarily to accommodate the traveling pub- lic, nighttime construction requires a fatigue-sensitive work zone that can necessitate positive physical barriers between the workers and the traffic. This requirement can change how tasks are performed compared to normal daytime practice. Tip Methods for managing fatigue and improving productivity during nighttime construction include the following: • Risk assessment and work activity modification. • Training, awareness. • Rest breaks, possibly even nap areas. • Physical activity. • Work-zone setup (bright light is effective). • Caffeine—the most widely used operational countermeasure for fatigue. Resource Fatigue Resource Directory, which was established by the Fatigue Countermeasures Group at the National Aeronautics and Space Administration (NASA) Ames Research Center, is available online at http://human-factors.arc.nasa.gov/zteam/. Productivity Measurement Techniques The productivity of nighttime construction operations requires good management techniques. Therefore, the following section discusses methods for productivity measure and modeling. Productivity Measurement The focus of many construction improvement programs is the acquisition of accurate and consistent labor productivity data. The quality of the data collected by these exercises usually depends on the data collection effort. There are many data sources, including historical records and previous productivity studies. The difficulty that most methods suffer from is a lack of consistency in the way they are per- formed. Noor (1998) critiqued and analyzed existing productivity measurement methods to develop practical and cost-effective productivity data collection methods that lead to consistent and accurate productivity data. Common productivity measurement techniques include those outlined in Table 5.1.

Productivity 53 Productivity measurements on transportation construction projects usually rely on records of materials and equipment usage. Labor productivity is rarely measured and recorded. This is partly due to the equipment-intensive nature of these projects. Tip Productivity measurement can be performed on a discrete or continuous basis. A strong cor- relation exists between the cost to obtain data and reliability of the data. The higher the reliabil- ity, the greater the costs to collect the data. Key Take-Away A wide variety of techniques can be used to measure labor productivity. The selection of the technique should consider reliability and cost. A midrange technique (such as activity sampling) requiring few measurements on multiple occasions during the work week is advised. Tip Analyses of productivity data can help define problems causing loss of efficiency on a project. Analyses can show the impact of factors on project progress, and can help in developing strate- gies to mitigate their effects. These analyses are neither difficult nor time consuming to perform using modern computer software and video equipment. Productivity Modeling Methods The data collected through productivity measurement efforts can be used to predict and esti- mate productivity. One interesting study by Boddy et al. (1986) demonstrated, in some instances, no systematic relationship between wages and labor productivity. Another important finding was that wages are related to productivity in the regular shifts but not during overtime periods. The study demon- strated that given a fixed crew size, productivity is more a function of downtime than relative wages. Key Take-Away Work-shift productivity was found to correlate more to the amount of downtime on a particular shift. Therefore, higher nighttime wages may not cause an increase in productivity. Management policy should focus on work planning to achieve continuity at night rather than on monetary incentives. Technique Method Notes Direct observation Continuous observation relies on a trained observer monitoring construction operations throughout the shift. The main shortcoming of this technique is that a single observer can monitor only a single crew with a predetermined maximum size. Work study Direct monitoring does not need to be for the entire day. Instead, the monitoring period corresponds to the length of the work cycle of the operation monitored. Audio- Visual Audio-visual techniques such as time-lapse photography and videography using movie and video cameras are used to acquire data. The advantage of audio-visual techniques is that they decrease the burden of data collection and create a permanent record of the activities. Activity sampling This technique consists of making observations of workers on a periodic basis. It relies on a snapshot of the activity being performed and the workers being studied. Table 5.1. Common productivity measurement techniques (Noor 1998).

54 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity Productivity Improvement Studies have indicated consistently that these are the priority areas for construction produc- tivity (Arditi 1985): • Planning and scheduling. • Labor management relations. • Site supervision. • Equipment policy. • Engineering design. The California Department of Transportation (Caltrans) has had several urban freeway rehabilitation projects that required around-the-clock construction operation to minimize the impact they had on motorists. These projects have provided data for evaluating productivity rates (Lee et al. 2007). The productivity studies investigated different lane-closure schemes and rehabilitation strate- gies. The results showed production rates and learning-curve effect were higher in cases where the roadbed was fully-closed and full lane widths rehabilitated compared to cases of partial closure and partial-width rehabilitation. Continuous slab replacement had a higher production rate and learning-curve effect than random slab replacements. These results imply that specified construction sequencing and phasing affect productivity. The study findings were unable to discern affirmatively the impact of nighttime activities alone on construction operations. Lee et al. used Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) to perform the analyses. Resource The CA4PRS software identifies optimal project work strategies that balance the construc- tion schedule with inconvenience to drivers and transportation agency costs. It is a versatile tool for analyzing the productivity effects of specified work sequences: http://www.fhwa.dot.gov/ research/deployment/ca4prs.cfm Productivity and Production Rates Various STAs have published production rates for important construction activities. Estab- lishing and adapting these rates is governed mostly by the FHWA guide for determination of construction contract time. While STAs have developed such productivity information, little guidance, specifically about nighttime construction production rates, is available. Resource The FHWA Guide for Construction Contract Time Determination Procedures is a valuable resource: http://www.fhwa.dot.gov/construction/contracts/t508015.cfm Most of the published STA data are overall production rates for an activity or pay item; this should be distinguished from labor, equipment, or crew productivity rates. In a sense, the pub- lished production rates are an aggregation of the combined productivity of labor, equipment, or crews used to perform the work. STAs collect production-rate data based on historic data found in inspection reports, which are not usually concerned with how effective contractor laborers are in performing the work. Productivity rates, on the other hand, describe the number of units of output that could be

Productivity 55 produced on a specific activity (such as concrete paving) by individual laborers (such as concrete finishers), equipment (such as the concrete paver), or crews (which are the combination of a specific piece of equipment and the labor needed to operate it). Detailed productivity rates for most labor, equipment, and crews can be found in the RSMeans construction cost data references. Key Take-Away Productivity versus Production Rates Productivity rates look at production per unit time of individual labor, equipment, or crews, while production rates published by STAs are overall rates of production for activities or pay items. Productivity rates provide more detailed information than overall production rates. Tip STAs usually have good data describing the labor, equipment, and crews used on projects, as well as their corresponding production. STAs can therefore establish nighttime productivity rates of labor, equipment, and crews similar to the daytime rates already produced. Illinois Department of Transportation (IDOT) Production Rates The IDOT Bureau of Design and Environment Manual lists production rates for major items (IDOT 2010). These rates are based on an average 8-hour work day. The manual states that the published rates should be reviewed periodically to adjust the rate for advancements in equip- ment outputs or construction techniques. The IDOT manual provides a low and a high value for the production rate of each item. The low rates are for small projects, while the high rates are for larger projects. Expedited projects need the published rates to be adjusted for longer working days, but the manual does not provide a method for making such an adjustment. Finally, the manual explains that rates much higher than those published could be achieved in particular situations. Again, there are no production rates specifically for nighttime work. Michigan Department of Transportation (MDOT) Production Rates Similar to Illinois, MDOT utilizes production rates published in its Construction Manual for calculating the overall contraction duration of projects. The origin of the published rates and their data is described. MDOT does maintain an accurate database of production records in a software system called Field Manager, which stores construction inspection records (Mattila and Dina 2003). Similar records of actual production records may be available at other STAs; however, an important fac- tor to consider is that these records need to include information about production-impacting factors such as project location, weather conditions, equipment and construction methods, size of job, and worker skill. Summary The main interacting elements that control nighttime work productivity are human factors, work-zone factors, and work management countermeasures. Human factors are mainly the effects of worker fatigue through three main pathways: number of hours at work, timing of

56 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity shift schedule, and task-specific demands of the work. These factors are controlled largely by the circadian process—human physiological rhythms and cycles. Work-zone factors, on the other hand, are the physical conditions, and primarily the lighting. Finally, work management countermeasures are the methods of on-site intervention that ensure worker safety and productivity, including the use of caffeine and naps to improve physi- ological alertness. Specific techniques are available to improve nighttime work productivity. These techniques include good lighting, planning and scheduling, labor management relations, and site supervi- sion. The CA4PRS software is a good tool that identifies strategies to balance the construction schedule with inconvenience to drivers and transportation agency costs.