The AASHTO Green Book (2) offers considerable flexibility in the use and design of medians. The Green Book (2) describes operational and safety advantages, provides appropriate widths for different functions, and discusses tradeoffs. The use of medians is clearly encouraged by the AASHTO Green Book (2). Nothing in the AASHTO Green Book (2), however, mandates the use of medians or their design dimensions. The AASHTO Green Book (2) offers considerable flexibility in the use and design of medians. The Green Book (2) describes operational and safety advantages, provides appropriate widths for different functions, and discusses tradeoffs. The use of medians is clearly encouraged by the AASHTO Green Book (2). Nothing in the AASHTO Green Book (2), however, mandates the use of medians or their design dimensions.

Designers should understand the functions and benefits of medians and be prepared to provide median design treatments that fit within the overall cross section. The width and design of medians offers flexibility for the designer. Median width can be adjusted as necessitated by available right-of-way constraints and border area needs. Medians should be wide enough to allow the design vehicle to safely make a selected maneuver and to provide space for appropriate safety devices.

From A Guide for Achieving Flexibility in Highway Design, 2004, by the American Association of State Highway and Transportation Officials, Washington, D.C. Used by permission. AASHTO publications may be purchased from that organization's bookstore at 1-800-231-3475 or online at http://bookstore.transportation.org.

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