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31 Geometric design criteria; U-turns are prohibited in some school zones. At signalized intersections; and U-turns are prohibited to relieve congestion at median If less than 11.3 m (37 ft) of width is available from openings. the inside of the left-turn curb to the curb of the oppos- U-turns are permitted at unsignalized median openings ing lanes. where a specific need is identified. U-turns are prohibited where a need is identified through Two agencies stated that U-turns are prohibited at all median engineering judgment. openings unless they are signed to permit U-turns. Some agencies that did not have formal policies on where to permit or prohibit U-turns have informal guidelines that MEDIAN AND ROADWAY WIDTHS TO are presented below: ACCOMMODATE U-TURN MANEUVERS U-turns are permitted only at locations having sufficient The minimum median and roadway widths required to roadway width for maneuver. accommodate U-turn vehicles are key factors in whether a U-turns are prohibited based on accident rate or safety U-turn movement is permitted at a median opening. About problems. half of the responding agencies stated that they follow the U-turns are prohibited at signalized intersections where AASHTO Green Book (3) to determine the median and road- right-turn overlaps are allowed. way widths required to provide for U-turns at unsignalized U-turns are prohibited where they would create a sub- median openings. Figure 13 illustrates these AASHTO crite- stantial number of conflicts. ria, based on Green Book Exhibit 9-92. Several agencies Figure 13. AASHTO minimum median widths to accommodate U-turns (3).