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Page 57
Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Page 59
Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Page 59
Page 60
Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Page 60
Page 61
Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Page 61
Page 62
Suggested Citation:"Chapter 6 - Quality." National Academies of Sciences, Engineering, and Medicine. 2012. A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity. Washington, DC: The National Academies Press. doi: 10.17226/22723.
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Page 62

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57 The most important advantage of nighttime construction and why it is used in most cases is to reduce congestion and delay for the traveling public during project construction. At the same time, it is essential for STAs to maintain the quality of nighttime construction operations paral- lel with the FHWA national objectives on quality construction, which are to improve system performance; decrease congestion and impacts on the environment; improve safety by minimiz- ing work-zone frequency, duration, and disruption of traffic flow; and improve the economic efficiency of highway investments. Many activities can be performed during nighttime construction, with road paving being the most common. According to research conducted by the National Quality Initiative (now the National Partnership for Highway Quality), pavement smoothness is one of the most sig- nificant measures used to judge the quality of the roads. This research has resulted in develop- ment of several quality programs, such as the FHWA HIgh PERformance Concrete PAVing (HIPERPAV) program, to ensure that quality in highway and road construction is met in terms of long-term performance expectations with the fewest maintenance and rehabilitation requirements. In addition, resources such as FHWA’s National Highway Specifications provide the frame- work for construction project evaluation and assessment, from the quality of materials to the final pavement smoothness (https://fhwapap04.fhwa.dot.gov/nhswp/). Al-Kaisy and Nassar (2003) surveyed STAs and IDOT districts. The results showed that 60 percent of the STAs having experience with nighttime construction believe night work had no impact on quality and five percent believe it actually resulted in better quality. As far as the Illinois DOT districts with nighttime construction experience, 88 percent reported that the quality of work at night was equal to or better than work completed during daylight hours. Key Take-Away “Quality of work does not seem to be affected by performing work at night” (Elrahman 2008). Studies on the quality of work produced at night versus during the day do not confirm the perception that the quality of nighttime work decreases. Price (1985) concluded that the quality of work does not experience significant degradation if the work was performed at night versus daytime. Hancher and Taylor (2000) and Al-Kaisy and Nassar (2002) concluded that cooler tem- peratures at night and longer working hours can actually increase nighttime work quality. Park et al. (2001) reported that the International Roughness Index (IRI) scores for paving operations were only 3 percent less at night than during the day. C H A P T E R 6 Quality

58 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity As more construction work is completed at night, it is important for transportation officials to understand and implement quality measures in nighttime construction. The following sections describe factors affecting nighttime construction quality inspections, quality of construction work at night, nighttime paving quality, and quality management programs adopted by agencies to maintain the quality aspect in nighttime work. Factors Affecting Nighttime Construction Quality This project’s survey of 14 STAs found the perception to be that some factors may increase quality, while others may reduce quality (see Table 6.1). However, some activities may benefit from a factor, while the factor may detract from others. The requirements for each task should be considered. Tip Adequate visibility and proper temperatures are required to produce quality nighttime asphalt paving. Nighttime work benefits from the low traffic volumes and cooler temperatures. Other impor- tant factors that have an impact on nighttime construction quality are as follows: • Inadequate lighting and poor vision. • Human factors. • Insufficient amount of inspection and supervision. Inadequate Lighting and Poor Vision Conducting nighttime work is challenging, especially with visibility as one of the issues. Work quality is highly dependent on the ability to see the work. Therefore, sufficient lighting of the work area is important for quality and safety. With sufficient lighting, the final outcomes of the project produce similar quality to daytime work. Each of the activities, when performed at night, may have its own visual requirement. Night- time activities, such as painting spots on pavement by marking machine operators, may require a higher visual requirement compared to activities such as spotting string lines by workers (Hyari and El-Rayes 2006b). Factor Reduce Quality (%) Same Quality (%) Increase Quality (%) Cooler temperature at night 50 36 14 Longer work hours at night 7 79 14 Lighting 86 14 0 Less interference of traffic 0 21 79 Quicker material deliveries 7 21 72 Allows more lanes to be closed 0 36 64 Increase duration of closed lanes 0 43 57 Effective communications among agency personnel, contract manager, and field staff 43 36 21 Availability and supply of materials and spare parts 57 36 7 Table 6.1. STA survey results on perception of factor impacts on quality.

Quality 59 Human Factors Nighttime workers often experience fatigue due to lack of sleep/rest, as well as issues adjusting to the idea of working at night. Fatigued workers may be unable to stay mentally alert and focus on their jobs. Insufficient Amount of Inspection and Supervision It is necessary to provide good supervision on nighttime construction activities. Good super- vision ensures that end products meet the specifications and standards, even though the work is conducted at night. In addition, inspectors should keep in mind the reflections made by lighting on asphalt pavement, as it greatly magnifies ridges and depressions. The Quality of Construction Work at Night Different types of construction and maintenance work are usually performed at night. In NCHRP Report 498, Ellis et al. (2003) concluded that nighttime highway work can be performed safely and with a level of quality and economy comparable to that achieved from daytime con- struction. The specifics tasks reviewed in that study are listed in Table 6.2. Some activities, such as bridge deck overlays, may be better suited for nighttime work and do not suffer in quality when performed at night. During the summer months, cooler temperatures at night help to enhance the quality of the concrete placement. Achieving a good concrete place- ment during the day can be difficult due to the high temperatures or direct sunlight, because they speed up evaporation and the setting of portland cement concrete. For instance, placing latex-modified concrete on bridge decks is considered a very suitable task to be performed dur- ing nighttime construction. Maintenance Task Performed at Night Construction Task Performed at Night Maintenance of earthwork/embankment Excavation—regular, lateral ditch, channel Reworking shoulders Embankment, filling, compaction Barrier wall or traffic separator Barrier wall or traffic separator Milling and removal Milling and removal Resurfacing Resurfacing Repair of concrete pavement Concrete pavement Crack filling Subgrade stabilization and construction Pot filling B ase courses—clay, cement, asphalt Surface treatment Surface treatment Waterproofing/sealing Waterproofing/sealing Sidewalk repair and maintenance Sidewalk construction Riprap maintenance Riprap placement Resetting guardrail/fencing Guardrail fencing Painting stripes/pavement markers Painting stripes/pavement markers/metal buttons Landscaping/grassing/sodding Landscaping/grassing/sodding Highway signing for maintenance works Highway signing for construction Traffic signal maintenance Traffic signal construction Highway lighting system repair and maintenance Highway lighting system construction Bridge deck rehabilitation and maintenance Bridge deck construction Damaged structures maintenance and rehabilitation Drainage structures, culverts, and sewers construction Sweeping and cleanup Construction of other concrete structures Table 6.2. Highway maintenance and construction tasks performed at night (Ellis et al. 2003).

60 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity Nighttime Paving Quality Studies by Hinze and Carlisle (1990a and 1990b) and Ellis and Kumar (1993) found that the quality of paving performed at night met smoothness specifications but can be less when com- pared to the quality of daytime paving. The Hinze and Carlisle study was based on questionnaires and not on actual project data. A Washington State Department of Transportation (WSDOT) project, on which a statistical analysis of the Profile Ride Index (PRI) (measured in mm/km or in./mi) was performed, revealed no differences between daytime and nighttime paving shift smoothness (Dunston et al. 2000). The contractor needs to exercise extra care and quality control when performing nighttime paving to ensure reasonable smoothness. Several methods are considered the most suitable to compare daytime versus nighttime paving quality. According to Douglas and Park (2003), the three methods used by the Oregon Department of Transportation (ODOT) are IRI, Composite Pay Factor (CPF), and Overall Condition Index (OCI). • IRI “measures longitudinal pavement profiles to evaluate pavement condition and remaining life.” • CPF is used to “measure, through statistical analysis, the quality of the material that contrac- tors produce and use during paving; resulting in the anticipated performance and quality of the pavement.” • OCI measures the pavement condition such as the amount of rutting, cracking, raveling, and bleeding present on pavements. Asphalt compaction is another construction activity during which quality can be affected at night. The effect of nighttime on compaction, however, is less significant than on surface smoothness. Compaction test results from a daytime paving project, I-70 in Colorado, were compared to those of a similar construction job done during nighttime hours on I-25 (Price 1986a and 1986b). It was felt initially that compaction performance might suffer due to cooler nighttime tem- peratures. However, compaction of night paving was just as high as that of day jobs and, in some tests, it was even higher. The overall quality of the work done on the nighttime project was very similar to a well-done day job (Rebholz et al. 2004). Paving at night can improve quality, primarily because material is delivered at a steady rate given the following: • Better production at night. • Less traffic to and from the jobsite. • Less interference from outside. • Less congestion at the plant when loading trucks. • Trucks have better turnaround time. • Rush-hour traffic avoided, morning and evening. The common perception among contractors, owners, and state officials is that the quality of nighttime asphalt paving, either repairs or overlays, obtained by using proper procedures, adequate inspection and testing, and strict grade control, compares favorably with the quality of the overlays constructed during daytime (Rebholz et al. 2004). Key Take-Away Of the 32 projects in 1998 that won National Asphalt Pavement Association Quality in Con- struction Awards, the majority, whether rehabilitation or new construction, involved night paving, restricted hours, or phased construction to limit disruption of traffic flow.

Quality 61 Quality Management Programs Most studies conducted indicate the quality of the finished product done under nighttime operations has not been significantly different from work performed during the daytime (Elrahman 2008). Regardless, contractors and agencies still need to exercise good quality management programs during nighttime construction. One of the most recommended and frequent practices is scheduled inspections. None of the agencies interviewed for this study indicated that the quality expectations were any different, or lower, for work performed at night. Similar to daytime construction, adequate inspection needs to be conducted to obtain quality work at night. Quality inspection may be conducted frequently or not, but the work/task needs to be monitored continuously. The inspection may be performed by the agency or its representative. Either way, it is necessary to ensure that adequate inspection is available by determining the need and frequency of the inspections, as well as the staff needed to perform the inspections. Advance planning is essential to ensure adequate inspectors are available for staffing nighttime projects. In addition to inspection of the work, the equipment used in nighttime construction should be inspected on a regular basis. Any devices that are dirty or impaired and result in low visibility compared to visibility with good-condition devices should be replaced immediately. Equipment inspection can be performed regularly prior to the start of nighttime work to avoid problems. Nighttime asphalt paving inspection challenges include the following: • Road alignment. • Mix issues, such as segregation. • Mix temperature—lumps. • Truck beds not clean—cannot see until too late. • Sampling mix is more difficult due to lighting—cannot see mix as well. Tip Be sure to inspect the devices used for nighttime work, as they might be satisfactory for daytime use but not nighttime because of inadequate visibility under headlamp illumination at night. Tip Maintain qualified inspection staff that are available for night reassignment on short notice to fill in as needed. Resource The American Traffic Safety Services Association (ATSSA) has a Comprehensive Inspection Training course on CD-ROM and offers a companion product to the training titled Quality Guidelines for Work Zone Traffic Control Devices. http://www.atssa.com/LinkClick.aspx?fileticket=zXPoddZMiD0%3D&tabid=64 Conclusions Most agencies report that nighttime construction quality is equal to or better than daytime work. A review of previous studies also makes it clear that the quality of nighttime construc- tion projects is comparable to that of daytime projects. One of the main reasons is that both

62 A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity daytime and nighttime projects have the same quality specifications, regardless of when the work is performed. However, lack of good lighting when conducting nighttime work may result in poorer work quality because work quality is highly dependent on the ability to see the work. Therefore, it is very important for transportation agencies to ensure sufficient lighting is in place when per- forming nighttime construction and inspecting the work. The need to maintain visibility should be discussed during pre-bid or pre-operation meetings. In addition, it is recommended that the quality assurance program for nighttime construction, such as scheduled inspection, be developed and implemented as needed to evaluate the overall quality and effectiveness of nighttime construction tasks. Consequently, the program also helps to identify areas in which improvement is needed to ensure that the quality specification of a task can be met.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 726: A Guidebook for Nighttime Construction: Impacts on Safety, Quality, and Productivity provides suggested guidance on the conduct of nighttime highway construction and maintenance operations.

These guidelines are based on best practices and strategies for nighttime operations that relate to the safety of workers and the traveling public as well as the quality of the as-built facility. The guide also addresses work-zone risk analysis planning and implementation, construction nuisances to both neighbors and workers, and work-zone illumination methods.

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