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Impact of Shoulder Width and Median Width on Safety (2009) / Chapter Skim
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Pages 9-16

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From page 9...
... Therefore, a prioritized list is needed to identify the relative significance of each geometric element. Given the current definition of design speed, it is probably the most critical design element to be selected since it has the potential to impact the values used for almost all other design elements (1, 5)
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From page 10...
... This section discusses the findings for these design elements. Several of the findings have been cross-referenced with the interim report from NCHRP Project 17-27, "Parts I and II of the Highway Safety Manual," (21)
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From page 11...
... The section of the HSM on multilane rural roads developed as part of NCHRP Project 17-27 (21) also proposed AMF values for lane width on rural multilane highways (see Table 2)
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From page 12...
... Additional procedures are available for roadways with lower volumes or different percentages. For divided highways, the draft HSM uses recommended values from NCHRP Project 17-29 (22)
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From page 13...
... The HSM section on multilane rural roads developed as part of NCHRP Project 17-29 (22) also proposes AMF values for rural multilane highways (see Table 5 in HSM)
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From page 14...
... . Several studies have focused on two-lane rural roads and have addressed issues relative to lane widths, shoulder widths and types, clear zones, and horizontal and vertical alignments.
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From page 15...
... The degrees of influence vary by design element and application and often are specific to a set of roadway conditions. There are current parallel efforts under way to address the quantification of the safety and operational impacts from design element trade-off.
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From page 16...
... Median width AMF for me dian width Median width (ft) 10 20 30 050 70 90 1.00 0.91 0.85 0.80 0.70 0.65 AMF for shoulder width is based on rural two-lane roads and from expert panel reco mme ndation Elvik and Vaa 2004 ( 36 )
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Key Terms

  • median width
  • shoulder width
  • nchrp project
  • rural roads
  • operational impacts

  • recommended values
  • design elements
  • nchrp report
  • safety manual
  • lane width

  • multilane rural
  • design element
  • panel recommendation
  • prior studies
  • paved shoulder

  • professional engineers
  • wider lanes
  • multilane roadways
  • rural multilane
  • texas council

  • tional impacts
  • crash occurrence
  • divided highways
  • appropriate design
  • research focus

  • wider medians


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