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Final Report for NCHRP Report 581: Design of Construction Work Zones on High-Speed Highways Copyright National Academy of Sciences. All rights reserved. 5 CHAPTER 1 INTRODUCTION 1.1 BACKGROUND Each year, state transportation departments reconstruct and rehabilitate thousands of miles of high-speed highways. To varying degrees, the associated construction activities require alteration of traffic patterns and the introduction of new features to the driving environment. Whereas permanent roads are designed solely to facilitate safe and efficient traffic movement, roadways in work zones must also accommodate mechanized and labor-intensive construction activity. The transportation and construction functions are often at cross-purposes; research indicates that crash rates in work zones are generally higher than those for the same site during normal operations (1, 2). As the portion of the capital funds committed to rehabilitation of roads increases, road user and road worker exposure to work zones will also increase. The public and transportation agencies are increasingly aware of the potential disruption that construction work zones can inflict on mobility and safety. Survey results published in 2001 indicate that work zones are the second leading cause of public dissatisfaction with highways (3). In 2004, the Federal Highway Administration (FHWA) promulgated an updated Work Zone Safety and Mobility regulation in response to a congressional directive. However, some of the technical resources needed to effectively manage the transportation system while providing for continual renewal and enhancement of the supporting infrastructure have not been widely available. Until recently, work zone design generally consisted of developing temporary traffic control plans. Temporary traffic control plans are critical to work zone safety and operational efficiency. However, the work zone challenge cannot be met with temporary traffic control alone. Transportation management and the design of supporting infrastructure for work zones are also necessary to mitigate the potential negative impacts of work zones. Up to this point, no guidance has been published with an intended use as national guidance for construction work zone design. The FHWA Manual on Uniform Traffic Control Devices (MUTCD) (4) is a national standard applicable to development of temporary traffic control plans. The AASHTO 2001 Policy on Geometric Design of Highways and Streets (Green Book) (5) is available and recognized nationally as the benchmark guidance publication for permanent roads. Many state DOTs have work zone design guidance and publications that guide design of construction work zones. These DOT publications vary in the scope and depth. Taking the various DOT publications together, there are areas of agreement and disparity on matters of substance. This research was undertaken to develop design decision guidance for any transportation agency involved in designing construction work zones on high-speed highways.
Final Report for NCHRP Report 581: Design of Construction Work Zones on High-Speed Highways Copyright National Academy of Sciences. All rights reserved. 6 1.2 RESEARCH SCOPE AND PRIORITIES The overall objective of the research was to develop a design decision methodology for construction work zones on high-speed highways. In delineating the project scope, a distinction was made between temporary traffic control and work zone design features. The principal work zone design decisions include work zone type, horizontal and vertical alignment, cross sectional elements and dimensions, roadside design and access points. All of the common work zone design features are covered by the design decision guidance. However, some aspects of work zone design are considered especially important or problematic and worthy of more intensive effort. During the preliminary phase of the research, detailed research plans were developed for the following topics: 1. Statistical Studies of Lane Shifts With and Without Lane Width Reductions; 2. Development of Roadside Safety and Roadside Barrier Placement Guidance; 3. Development of a Speed Profile Model in Construction Work Zone Using Artificial Neural Networks; 4. Performance of Heavy Trucks in Construction Work Zones; 5. Influence of Design Features on Driver Performance; 6. Analyzing Work Zones Using Simulation. Based on the priorities expressed by state DOTs through the survey, available resources, and other considerations, the panel directed that studies 2 and 3 be conducted. Further refinement of the research and scope of the design decision guidance was accomplished through a literature review and survey of state departments of transportation (DOTs). A review of published research indicated a limited number of established relationships between work zone design decisions and the probable safety and operational consequences. DOTs were surveyed on their work zone criteria, practices and design guidance needs. Collectively, these information sources indicated that work zone speeds are an ongoing concern for transportation agencies. The concerns cover the gamut of potential inconsistencies between speeds in the work zone and the approaches, speeds used in the design process and observed speeds, and posted and observed speeds. However, the highest priority expressed through the survey of state DOTs was for improved barrier placement guidance. Based on the preliminary assessment, it was concluded that the comprehensive design guidance should cover work zone design decisions not fully addressed by other publications, specifically the MUTCD and the AASHTO Roadside Design Guide (6). Developing new guidance for use in conjunction with other publications was determined to be a more appropriate use of resources than supplanting or duplicating existing, accepted publications. To address the identified gaps and priorities, emphasis was placed
Final Report for NCHRP Report 581: Design of Construction Work Zones on High-Speed Highways Copyright National Academy of Sciences. All rights reserved. 7 on development of a speed prediction model for common freeway construction work zone types and design guidance for barrier placement. 1.3 ORGANIZATION OF THIS REPORT This report provides an overview of work zone issues for high-speed highways and in-depth review of subjects related to work zone design and safety. Previously completed work zone safety and operations research was reviewed, assessed and summarized in Chapter 2. Construction work zone design guidance applicable to high- speed highways was identified, reviewed and summarized in Chapter 3. This includes publications with national applicability, state DOT design guidance publications, and information gleaned from responses to the state DOT surveys. Chapter 4 explains and documents how the research products were developed. Chapter 5 provides conclusions and recommendations. This research resulted in two products intended for use by agencies in establishing work zone design policies and criteria and by practitioners in making project-level work zone design decisions. Appendix A is the comprehensive design decision guidance for construction work zones on high-speed highways. It consists of six chapters and is self- standing. The rationale for the guidance is included in the body of the research report, primarily in Chapter 4. The second research product is the speed prediction model, which is in Appendix B and is presented on a compact disc (CD). The model will run on Microsoft Windows-equipped computers and has a Microsoft Excel user interface. Predicted speeds are graphically plotted in the form of speed profiles. A userâs manual is also included.
