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Project Development Workflow Tasks (PDWT)
Part 3 - Identify Project Need and Project Initiation Document
II. Project Initiation Document
B. Develop Initial Alternatives (150.10) - Develop Concept Alternatives (WBS 150.10.15)
Median barrier warrants were established through extensive study of freeway cross-median accidents. The Headquarters Office of Highway Safety Improvement Program annually monitors cross-median accidents and prepares an annual report. The annual report is available on the Highway Safety Improvement Program website. Median Barrier projects are initiated when the Traffic Operations Branch has conducted a study and determined that median barrier is warranted. For other types of projects where median barriers may be a consideration, the project engineer may request the District Traffic Operations Branch to investigate and make recommendations on median barrier need and type. Chapter 7-04 of the Traffic Manual discusses median barrier warrants for freeways and non-freeways.
For freeways, the median width, ADT and number/severity of cross-median type accidents are used to determine if the warrants are met. Figure 7-7 of the Traffic Manual indicates the need for median barrier based on median width and ADT. A Traffic Accident Investigation is required to analyze the accident history.
Median barriers may also be an appropriate solution to cross-median accidents on multi-lane (two or more lanes in each direction) expressways and multi-lane conventional highways. The volume/median width and accident study warrants apply to freeways only, but they may be used as a guide for non-freeways. However, a problem is created at intersection openings in the median barrier and may require special end-treatments. Careful consideration of the number of intersections, accident history, alignment, driveways, grade, and sight distance as well as traffic volumes and median width must be given for non-freeway installations. It is the engineer's responsibility to determine, decide, and document the best improvements.
Once a decision has been made that a median barrier is warranted, then the type of median barrier must be selected. The approved standard types of median barriers for new installation are: (1) concrete median barrier, and (2) thrie beam barrier (single or double). Headquarters approval is required for any new installation or reinstallation of metal beam barrier or cable barrier. Choice of median barrier type is covered in the Traffic Manual Chapter 7-04.4 Criteria for Choice of Type and the Median Barrier Policy memo (Median Barrier Types to be Used in Highway Medians) dated July 18, 2001.
Cost of the installation of the barrier varies vastly depending upon many design factors. Chapters 7-04.5 through 7-04.8 of the Traffic Manual discuss many of the design issues that need to be addressed.
The headquarters Office of Landscape Architecture can provide guidance on barrier aesthetics.
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This page last updated October 20, 2010