Roundabout Practices (2016) / Chapter Skim
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From page 16... ...
16 were built as part of projects overseen by their state agency on the state highway system. Table 5 displays the approximate total number of roundabouts, by type, as reported by each state responding to the questionnaire, and Table 6 displays the approximate total number of roundabouts on the state highway system, by type, as reported by each state.
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17 single-lane and multilane roundabouts. Rural roundabouts are most likely to be single-lane roundabouts.
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18 States were also asked to provide additional reasons why roundabouts were selected in a comment field. Figure 24 displays the most frequent reasons for the selection of roundabouts by state agencies.
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19 Reported Mini-Roundabouts on the State Highway System Reported Single-Lane Roundabouts on the State Highway System Reported Multilane Roundabouts on the State Highway System Reported Total Roundabouts on the State Highway System Alaska 0 11 7 18 Arkansas 0 0 4 4 California 0 11 12 23 Connecticut 0 3 1 4 Delaware 1 11 1 13 Florida 0 11 3 14 Georgia 2 20 0 22 Idaho No answer No answer No answer -- Illinois No answer No answer No answer -- Indiana 0 5 9 14 Iowa 0 7 0 7 Kansas 0 13 7 20 Kentucky No answer 9 9 Louisiana 0 22 1 23 Maine No answer 19 5 24 Maryland 1 53 24 78 Massachusetts 0 4 2 6 Michigan 0 10 15 25 Minnesota 0 24 9 33 Mississippi 0 3 3 6 Missouri 1 55 15 71 Montana 0 10 10 20 Nebraska No answer 6 2 8 Nevada No answer 4 No answer 4 New Hampshire 0 8 1 9 New Mexico No answer 10 10 20 New York 0 65 25 90 North Carolina 0 120 16 136 North Dakota No answer 1 No answer 1 Oregon 0 1 1 2 Pennsylvania 0 17 1 18 Rhode Island No answer No answer No answer -- South Dakota 0 0 0 0 Texas No answer No answer No answer -- Vermont 0 6 1 7 Virginia No answer 110 5 115 Washington 4 80 30 114 West Virginia 0 0 4 4 Wisconsin 0 100 147 247 Wyoming 0 5 0 5 Total 9 834 371 1,214 The number of roundabouts shown are numbers provided by each reporting state, and may differ from information included in the Literature Review section of this synthesis. -- = Not Reported.
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20 As with NCHRP Synthesis 264, state agencies that had not built a roundabout were asked to provide reasons. Because only one state agency had not built or planned to build a roundabout, compared with 35 state agencies in NCHRP Synthesis 264, the results are less meaningful.
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21 of the reporting states (10%) indicated they had not developed any public outreach material.
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22 have developed their own tools, including spreadsheets implementing HCM 2010 equations. Further, several state representatives commented that they specify different tools for the analysis of different time periods (existing versus future)
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23 Use of NCHRP Report 672 States were asked the extent to which their agency uses NCHRP Report 672 for roundabout design guidelines. As shown in Table 13, 11 states use only NCHRP Report 672, 10 use material from other sources to supplement it, and 13 have developed their own guidance to supplement it.
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From page 24... ...
24 or more than 20 years, is not common, and a design-life of 10 years is used by only a few state agencies. Design Vehicle Accommodation States were asked if their agency had developed guidance on the accommodation of large vehicles (trucks, emergency Design-Life Criteria Reporting State Agency Responses % Case-by-Case Basis 7 18 Practical Design Policy 4 11 Specific Criteria 0 0 Fixed Design Year 0 0 Fixed Duration 29 76 TABLE 15 ROUNDABOUT DESIGN LIFE CRITERIA REPORTED AS USED BY STATE AGENCIES 0 5 10 15 20 25 30 10 years 15 years 20 years 25 years 30 years FIGURE 26 Number of reporting states indicating roundabout design life used by state agencies with a fixed design-life duration.
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From page 25... ...
25 vehicles, farming equipment, oversize/overweight vehicles, etc.) at roundabouts.
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