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Human Factors Guidelines for Road Systems - Collection C: Chapters 16, 17, 18, 19, 20, 22 (Tutorials 4, 5, 6), 23 (Updated), 24, 25, 26 (Updated) (2010) / Chapter Skim
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Effects of Roadway Factors on Speed
Pages 15-16

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From page 15...
... Design Guidelines The following factors that appear to be associated with drivers' choosing a higher travel speed should be considered when designing roadways. Strength of Factors Associated with Empirical Evidence HIGHER Free-Flow Speeds Low-Speed Rural Highways Urban Streets Higher Design Speed Solid Solid Grade Solid Solid Wider Lane Width -- Mixed Higher Access Density Solid Mixed Separated Bicycle Lanes -- Mixed Less Pedestrian/Bicycle Side Friction -- Mixed No Roadside Parking -- Mixed Number of Lanes Solid - Shoulder Width Mixed - Based Primarily on Based Equally on Expert Judgment Based Primarily on Expert Judgment and Empirical Data Empirical Data 17-6
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From page 16...
... Roadside factors were not significant for the straight road sections, but accounted for about 40% of the variability in the speed data for curves. Additional analyses conducted without using posted speed limits resulted in only lane width as a significant variable for straight road sections, with both median presence and roadside development as significant variables for curves.
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Key Terms

  • speed limits
  • roadway factors
  • lane width
  • straight road
  • road sections

  • speed data
  • straight section
  • percentile speed
  • cross section
  • empirical data

  • expert judgment
  • influence speed
  • enforcing speed
  • speed typically
  • roadway sections

  • speed limit
  • driver speed
  • using posted
  • design speed
  • lowering speed

  • rural driving
  • curve sites
  • median characteristics
  • behavioral framework
  • factors listed

  • roadside details
  • guideline table
  • roadside factors
  • design consistency
  • multiple regression


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