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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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Tutorial 5: Determining Appropriate Sign Placement and Letter Height Requirements
Pages 66-69

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From page 66...
... This extra time is to account for the extreme viewing angle immediately before the driver passes the sign, which prohibits reading. If the maneuver has already begun, the driver does not need to continue to read the sign, and thus does not need more time.
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From page 67...
... Maneuver distances required for preparatory lane changes. Operating Speed (mi/h)
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From page 68...
... The legibility distance is calculated using the formula below: Legibility Distance = Information Presentation Distance - Advance Placement Step 6. Calculate the Minimum Letter Height The minimum letter height is the height required for the letters on the sign based upon the legibility distance calculated above.
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From page 69...
... = Reading Distance + Decision Distance + Maneuver Distance = 569 ft 5. Legibility Distance = Information Presentation Distance ­ Advance Placement = 569 ft ­ 200 ft = 369 ft 6.
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Key Terms

  • legibility distance
  • presentation distance
  • maneuver distance
  • information presentation
  • legibility distances

  • decision distance
  • reading distance
  • letter height
  • lane change
  • advance placement

  • minimum letter
  • traffic control
  • sign placement
  • daytime legibility
  • distance requirements

  • lane changes
  • control devices
  • gap search
  • base reading
  • change distance

  • distance required
  • devices handbook
  • deceleration distance
  • maneuver distances
  • greatly reduced

  • calculating base
  • handbook outlines
  • preparatory lane
  • distances vary
  • sign based


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