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NCHRP Report 627: Traffic Safety Evaluation of Nighttime and Daytime Work Zones (2008)
National Cooperative Highway Research Program (NCHRP)

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Finley, Melisa D, Ullman, Gerald L, Bryden, James E, Srinivasan, Raghavan, Council, Forrest M, Transportation Research Board. "Summary of Findings." NCHRP Report 627: Traffic Safety Evaluation of Nighttime and Daytime Work Zones. Washington, DC: The National Academies Press, 2008.

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Page
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Front Matter (R1-R10)
Summary (1-3)
Work Zone Effects on Traffic Safety (4-4)
Nighttime versus Daytime Work Zone Crashes (5-5)
Implications for This Study (6-6)
Study Overview (7-7)
Data Reduction and Analysis (8-8)
Work Zone Traffic Crash Analysis (9-11)
Work Zone Construction Accident Analysis (12-12)
Summary of Findings (13-13)
Study Methodology (14-14)
Data Collection (15-17)
Data Analysis (18-18)
Increases in Traffic Crashes Occurring during Nighttime and Daytime Work Activities (19-25)
Types of Crashes Occurring during Nighttime and Daytime Work (26-29)
Summary (30-33)
Chapter 4 - Recommended Management Policies, Procedures, and Practices to Improve Nighttime and Daytime Work Zone Safety (34-34)
Improvements in Maintenance and Construction Practices (35-36)
Nighttime Work (37-37)
Transportation Demand Management Programs to Reduce Traffic Volumes Through Work Zones (38-39)
Strategies to Improve Work Zone Traffic Control Devices (40-42)
Strategies to Improve Work Zone Design Practices (43-44)
Strategies to Improve Driver Compliance with Work Zone Traffic Controls (45-46)
Strategies to Develop Procedures to Effectively Manage Work Zones (47-47)
Summary (48-49)
Categories of Critical Data Elements (50-50)
MMUCC Guideline-Based Enhancements to State Crash Reports (51-51)
Selecting a Work Zone Crash Data Source (52-53)
State Highway Agency-Based Crash Data Collection and Reporting (54-54)
MMUCC Guideline Data Elements and Attributes - 2003 Edition (55-55)
Suggested Revisions to MMUCC Guideline Definitions (56-56)
Inherent Limitations in the MMUCC Guideline (57-58)
Data Element Considerations of Highway-Agency-Based Crash Reporting Systems (59-60)
Recommended Work Zone Crash Data Analysis Methods (61-61)
Summary (62-64)
Nighttime and Daytime Work Zone Effects on Crashes and Worker Accidents (65-65)
Work Zone Crash Data Elements, Collection and Storage Techniques, and Analysis Methods (66-66)
Recommendations (67-67)
References (68-70)
Appendixes A, B, C, and F (71-71)
Appendix D - Suggested Revisions to MMUCC Guideline Definitions (72-73)
Appendix E - Florida, Louisiana, and Maryland Agency Work Zone Crash Reporting Forms (74-78)
Abbreviations used without definitions in TRB publications (79-79)

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13 Table 7. NYSDOT construction worker for night work operations. These findings pertain to both accident types. traffic crashes and construction accidents. Accident Type Daytime Nighttime Accidents Accidents · About half of daytime work zone traffic crashes and 60 per- (n = 931) (n = 114) cent of nighttime work zone crashes on NYSDOT freeways Falls ­ Elevated 4.1% 6.2% Slip/Trip Strain 17.6% 18.6% and expressways occur during traffic lane closures. This Accident with Tool or Material 30.4% 27.4% statistically significant increase in lane closure crashes at Worker Hit by Equipment or night is probably the result of the higher relative frequency Construction Vehicle 6.3% 7.1% Other Equipment or Vehicle Accident 8.5% 13.3% of lane closure operations at night, rather than a higher Utility Contact 26.4% 17.7% crash risk. Other Accident 6.7% 9.7% · Overall, there appears to be little difference in traffic crash Chi-Square Test Results Daytime and nighttime distributions are not severity between daytime and nighttime work operations significantly differenta on freeway and expressway facilities. However, worker- a X2 = 4.523 < X 2 Crit (6, 0.025) = 12.592 involved traffic crashes at nighttime work zones were sig- nificantly more severe than in daytime. It should be noted that worker "involvement" did not necessarily imply that nighttime work activities and account for 6 to 7 percent of all the worker was struck by the vehicle; the higher percentage construction worker accidents. of severe crashes at night was often drivers or passengers in the vehicle rather than the worker. If a worker was struck, Severity of Construction Worker Accidents it usually resulted in an injury regardless of whether it oc- curred during the day or at night. The severity of construction accidents occurring during day- · Rear-end collisions comprise a smaller proportion of work time and nighttime work operations is compared in Table 8. zone traffic crashes at night work zone operations than dur- During night work, a slightly greater percentage of construc- ing daytime operations. This result is consistent with ex- tion accidents resulted in injuries than during daytime work, pectations that moving work activities to nighttime hours although this small difference is not statistically significant. reduces congestion and queuing that can lead to higher It is particularly noteworthy that only three worker fatalities rear-end crash frequencies. Also, working at night does not resulted from construction accidents over a 6-year period appear to result in more serious rear-end crashes (when (0.3 percent of 931 reported accidents), and they all occurred they do occur) than during daytime work operations. in daytime operations. · Crashes involving workers, construction vehicles or equip- ment, and construction materials and debris (both intrusion and non-intrusion crashes) comprise a greater percentage Summary of Findings of crashes at night than during the day. Intrusion crashes The following key findings are drawn from the NYSDOT involving workers (those of most concern to agencies and work zone accident database regarding work zones on free- highway contractors) are a higher percentage of crashes at way and expressway facilities, which are most often targeted night than during daytime hours. However, they are only a small proportion of the total work zone crash experience in either time period. Table 8. NYSDOT construction worker · Intrusion crashes at nighttime work operations for all types accident severity. of traffic control combined are significantly more severe than Injury Severity Daytime Nighttime at daytime work operations. A similar trend is evident for Accidents Accidents lane closure crashes, although the differences between night- (n = 931) (n = 114) Fatal 0.3% 0.0% time and daytime conditions are not statistically significant. Injury 65.2% 73.5% · The types of construction worker accidents occurring at None/PDO 34.5% 26.5% NYSDOT freeway and expressway work zones do not differ Chi-Square Test Results Daytime and nighttime distributions are not significantly between daytime and nighttime operations. significantly different a · The severity of construction worker accidents does not dif- a X2 = 2.846 < X 2 Crit (1, 0.025) = 3.841 fer significantly between daytime and nighttime operations.