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28 TABLE 10 Response rate for the highway agency survey Number of questionnaires Number of responses Response Agency type mailed received rate (%) State agencies 50 35 70.0 Local agencies 109 30 27.6 Total 159 65 40.9 Spacing for such locations must use alternate routes, some of which may involve making U-turns at nearby median openings. Approximately one-half of the state and local highway Other highway agencies are replacing conventional median agencies have formal policies concerning the minimum spac- openings that allow all traffic movements with directional ing between median openings. Most of the states and one of median openings that allow only U-turn movements or allow the local agencies that responded have different policies for only left-turn ingress to abutting developments; the left-turn rural and urban areas. egress movements would be made by turning right onto the Tables 11 and 12 present median opening spacing policies of arterial road and then making U-turn maneuvers downstream. state and local highway agencies, respectively, that had numer- ical spacing policies that could be easily summarized. Some agencies had policies based on more variable criteria (e.g., left- Consideration of U-Turn Maneuvers turn queue lengths, sight distance, and traffic volumes), which are harder to summarize and are not included in the tables. In the survey questionnaire, highway agencies were asked Table 11 shows that the states that have different spacing if they have a formal policy for designing and locating median policies for rural and urban areas typically require higher openings that makes specific reference to U-turn maneuvers. median opening spacing in rural areas than in urban areas. Only 16 percent of responding highway agencies indicated The values reported for minimum median opening spacing that they had a formal policy that addressed U-turn maneuvers. for rural areas varied from 152 to 805 m (500 to 2,640 ft), Most of these agencies rely primarily on AASHTO geometric while the comparable minimum spacing for urban areas var- design policies or some variation of AASHTO policy in their ied from 91 to 805 m (300 to 2,640 ft); however, the average own guidelines. The factors mentioned in the policies for minimum median opening spacing was 427 m (1,400 ft) in U-turn maneuvers at unsignalized median openings include rural areas and 268 m (880 ft) in urban areas. Table 12 presents the minimum spacing between median Median width (based on design vehicles and potential openings for the local agencies that presented quantitative for encroachment); minimum median opening spacing values in response to the Traffic conditions, including ADTs, truck volumes, and survey. The general trend of higher minimum median open- peak-hour turning movement counts; ing spacing at rural areas was still present, although the dif- Sight distance; ferences in median opening spacing between area types are Ability to begin and end U-turn maneuvers on the inner not as large as those for state agencies. lane next to the median; Accident frequency, particularly angle and rear-end col- lisions involving left- or U-turning vehicles; Left-Turn Treatments Specific threshold accident history criteria, such as five Most of the responding agencies require installation of left- or more left-turn or U-turn-related accidents per year, turn lanes at unsignalized median openings in all or most similar to MUTCD requirements; cases. Some agencies stated that left-turn lanes are provided Location of the median openings with respect to signal- only where specific warrants are met; most respondents indi- ized intersections; cated that their warrants were based on left-turn volumes. Only Presence of exclusive left-turn lanes; and two agencies responded that they have a formal policy on the Availability of alternate locations for left- and U-turn conditions under which direct left-turn access to intersections maneuvers. or driveways is replaced by indirect left-turn treatment. Prohibition of U-Turn Maneuvers TREATMENT OF U-TURNS AT MEDIAN OPENINGS Highway agencies were asked whether U-turn maneuvers were permitted or not permitted at the following types of Many state and local transportation agencies install nontra- median openings: versable medians on multilane arterial highways to improve safety and travel times, often denying the opportunity for Median openings on rural highways, direct left-turn access to certain properties. Traffic destined Median openings on urban/suburban arterials,

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29 TABLE 11 State policies on minimum spacing between median openings Minimum spacing (ft) State Rural Urban Comments Alabama 600 300 Arizona 1,320 660 For businesses generating high traffic volumes the minimum spacing is 330 ft California 1,640 1,640 Unsure of possible differences between rural and urban criteria Florida 1,320 330-660 Directional 2,640 660-1,320 Conventional Georgia 1,320 660 Maximum spacing 5,200 ft in rural areas and 1,320 ft in urban areas Iowa 1,000 660 Idaho 1,312 660 Illinois 2,625 (minimum) 1,312 Longer minimum 5,250 (desirable) spacing used if needed to accommodate left turn lanes Louisiana 1,500 500 Maine 1,312-1,640 (minor arterial) Criteria apply to 1,640-1,968 (major arterial) signalized median openings only Michigan 1,320 660 Desirable spacing Mississippi 1,760 880 North Carolina 1,500 700 (< 45 mph) Urban spacing criteria 1,000 (45-55 mph) vary with operating speed Nebraska 1,000 (minimum) 600 2,000 (desirable) New Mexico 600 300 Nevada 660 In urban areas, have criteria for access spacing rather than median opening spacing Ohio Have spacing criteria for driveways but not for median openings Oklahoma 2,640 (minimum) 1,320 Longer minimum 5,280 (desirable) spacing used if needed to accommodate left turn lanes Pennsylvania 1,500 1,500 South Carolina 1,000 500 Texas 1,320 2,640 1,320 2,640 Virginia 700-1,000 (35-45 mph) 700-1,000 (35-45 mph) Urban spacing criteria 500-650 (50-70 mph) 500-650 (50-70 mph) vary with design speed Range 500 2,640 300 2,640 Average 1,400 880 Unsignalized median openings, and The agencies with formal policies concerning when to Signalized median openings. prohibit U-turns at median openings do so in the following situations: Table 13 summarizes the agency responses. Approximately 80 percent of the agencies that responded permit U-turns at At all signalized intersections that have a right-turn over- all types of median openings. Nine agencies generally pro- lap phase from a side-street approach on the left during hibit U-turn maneuvers at unsignalized median openings. the protected left-turn phase on the mainline roadway;

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30 TABLE 12 Local agency policies on minimum median opening spacing Minimum spacing (ft) County Rural Urban Comments San Diego, CA 600 Springfield, MO 500 Fargo, ND 600 (arterials) 300 (collectors) Concord, NH 500 (commercial) For arterials and 1,000 (suburban) collectors Henderson, NV 660 Maricopa County, AZ 660 660 For arterials and collectors Pima County, AZ 1,320 1,320 Riverside County, CA 330-1,320 330-1,320 Based on intersection spacing Osceola County, FL 1,320 330-660 Directional 2,640 660-1,320 Conventional Broward County, FL 660 660 Range 660 2,640 330 1,320 Average 800 725 At any curve or on the approach to or near the crest of a At intersections with a receiving pavement width of 7.3 m grade where a U-turning vehicle cannot be seen by the (24 ft) or less and at which the average vehicle cannot exe- driver of any other vehicle approaching from any direc- cute a U-turn maneuver in a single continuous movement; tion within 150 m (500 ft) and at any intersection that At any location for which a review of accident history does not meet the minimum sight distance criteria stan- finds that a U-turn restriction should be implemented, dards for U-turns as established by AASHTO; possibly only for certain times of the day; TABLE 13 Number of highway agencies that permit U-turns at specific types of median openings Number (percentage) of agencies that permit U-turns at specific types of median openings Agency type U-turns permitted U-turns not permitted Total Median Openings on Rural Highways State agencies 26 (83.9) 5 (16.1) 31 a Local agencies 4 (100.0) 0 (0.0) 4 Total 30 (85.7) 5 (14.3) 35 Median Openings on Urban Highways State agencies 26 (83.9) 5 (16.1) 31 Local agencies 22 (84.6) 4 (15.4) 26 Total 48 (84.2) 9 (15.8) 57 Unsignalized Median Openings State agencies 26 (83.9) 5 (16.1) 31 Local agencies 22 (84.6) 4 (15.4) 26 Total 48 (84.2) 9 (15.8) 57 Signalized Median Openings State agencies 25 (80.6) 6 (19.4) 31 Local agencies 20 (76.9) 6 (23.1) 26 Total 45 (78.9) 12 (21.1) 57 a Includes county agencies only.