The National Academies

NCHRP 17-30 [Completed]

Traffic Safety Evaluation of Nighttime and Daytime Work Zones

  Project Data
Funds: $500,000
Research Agency: Texas A&M University
Principal Investigator: Dr. Gerald L. Ullman
Effective Date: 5/1/2004
Completion Date: 7/31/2008


The Intermodal Surface Transportation Efficiency Act established a documentation procedure for crashes in work zones for daytime and nighttime operations. Yet the various crash databases maintained by state DOTs and other agencies (for example, the Fatal Analysis Reporting System [FARS]) fail to yield data that can lead to explicit conclusions concerning the relative danger of nighttime construction operations versus daytime operations. The data are plagued by uncertainties on issues such as (1) the level of detail contained in the data, (2) the relationship of crashes to specific work-zone locations, and (3) the variation in reporting practices. Cottrell, B.H., Jr. "Improving Night Work Zone Traffic Control," Virginia Transportation Research Council, August 1999, concluded that, "although there is a perception that night work zones are less safe than daytime work zones, evidence to substantiate this perception, such as higher accident rates, was not available because of lack of traffic exposure data." Information is needed to assess the characteristics of these crashes in both daytime and nighttime work zones.

Recent research suggests that nighttime work zones have traffic-related crash rates up to three times higher than daytime work zones. If in fact nighttime operations are as dangerous as the data and perceptions suggest, more significant resources should be directed at ensuring worker and driver safety in nighttime work zones. The importance of this issue is magnified by recent operational efforts by DOTs to increase nighttime work operations in order to decrease work-zone traffic congestion.


The objectives of this research are to (1) determine the crash rates for nighttime and daytime work zones, (2) determine the nature of traffic-related crashes in nighttime and daytime work zones and identify similarities and differences, (3) develop management practices that promote safety and mobility in nighttime and daytime work zones, and (4) develop work-zone crash reporting recommendations to further improve the data collected on work-zone crashes.


Accomplishment of the project objectives will require at least the following tasks. (1.) Conduct a literature review to identify practices, processes, and policies currently used to increase work-zone mobility and safety and to determine the types and locations of work-zone crashes. (2.) Survey the states to identify crash report forms used by state police and crash reports completed by others, including but not limited to contractors and DOT construction, traffic, and maintenance personnel. Identify processes, data elements, and management procedures that could have application in assessing and improving work-zone safety. (3.) Identify sources of available work-zone crash data and traffic volumes based on a multi-year history to determine crash rates for nighttime and daytime work zones. (4.) Submit an interim report summarizing the findings of Tasks 1 through 3, including a revised work plan to be executed in Task 6. The work plan shall include, but is not limited to proposed sources of crash data, a plan for collecting supplemental data (if needed), and the data-analysis method (s).
(5.) Meet with the NCHRP panel to review the Task 4 interim report approximately 2 months after its submittal. Submit a revised interim report based on the panel's review. (6.) Execute the approved work plan to accomplish the four project objectives. (7.) Develop a list of critical data elements for work-zone crash reports and develop recommendations for data collection, storage, retrieval, and analysis procedures. (8.) Refine and develop additional management practices that may be used to mitigate nighttime and daytime work-zone factors that contribute to crashes. (9.) Submit a final report documenting the entire research effort. The final report shall describe how the project was conducted and include as appendices the list of critical data elements (Task 7) and management practices (Task 8).

Status: The project has been completed and the final report published.

Product Availability: NCHRP Report 627: Traffic Safety Evaluation of Nighttime and Daytime Work Zones 

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