Safety of U-Turns at Unsignalized Median Openings (2004) / Chapter Skim
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Pages 27-32
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From page 27... ...
The questionnaire addresses highway agency policies concerning location and design of median openings, treatment of U-turns at median openings, traffic operational and safety problems at median openings, and effectiveness of various mitigation measures. SURVEY RECIPIENTS The mailing list for the survey consisted of • 50 state highway agencies and • 109 local highway agencies (94 cities and 15 counties)
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Prohibition of U-Turn Maneuvers Highway agencies were asked whether U-turn maneuvers were permitted or not permitted at the following types of median openings: • Median openings on rural highways, • Median openings on urban/suburban arterials, Agency type Number of questionnaires mailed Number of responses received Response rate (%) State agencies 50 35 70.0 Local agencies 109 30 27.6 Total 159 65 40.9 TABLE 10 Response rate for the highway agency survey
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Approximately 80 percent of the agencies that responded permit U-turns at all types of median openings. Nine agencies generally prohibit U-turn maneuvers at unsignalized median openings.
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9 (15.8) 57 Unsignalized Median Openings State agencies 26 (83.9)
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About half of the responding agencies stated that they follow the AASHTO Green Book (3) to determine the median and roadway widths required to provide for U-turns at unsignalized median openings.
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Some of the mitigation measures for safety and operational problems cited are as follows: • Removal of closely spaced median openings by replacing raised medians with TWLTLs; • Replacement of conventional crossovers with directional crossovers; • Installation of left-turn storage lanes; • Installation of left-turn lanes with positive offset; • Signalized intersections; • Closure of median openings to allow left turns to align properly; • Reconfiguring of median openings by channelizing or adding left-turn lanes to prevent congestion or confusion in the median opening; • Installation of directional median openings to permit left turns from the major-road left-turn lane, but prohibit left turns and through movements from the minor road; • Provision of a median opening at what formerly was a right-in/right-out driveway; • Elimination of conventional median openings and replacement with jughandle U-turns; • Installation of "No U-turn" signs; and • Installation of raised/extended median to prevent U-turns. Six of the agencies that constructed improvement projects indicated that they have conducted a formal before-and-after evaluation.
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