Length Requirements for New Single-Arc Unsymmetrical Vertical Curve: Crest Type

Traditional unsymmetrical vertical curves consist of two parabolic arcs smoothly connected at the point of common curvature. A new single-arc unsymmetrical vertical curve that takes the form of a cubic instead of parabolic function has been recently developed. The curve has a rate of change in grade that gradually varies between the start and end of the vertical curve. The single-arc curve eliminates the sudden change that exists in curvature of traditional two-arc unsymmetrical vertical curves. This paper first develops the sight distance (SD) relationships for the new single-arc curve (crest type). With these relationships, the SD profile for the new curve is established and its shape shows a substantial improvement over the abrupt-type SD profiles of the two-arc curves. The length requirements that satisfy stopping, passing, and decision SD guidelines of AASHTO are then presented. Some examples are used to illustrate the use of the developed design aids. The new single-arc curve builds on previously developed unsymmetrical vertical curves to improve curve characteristics that hopefully will promote road safety.

• Record URL:
  • https://doi.org/10.3141/2060-05
• Summary URL:
  • http://scholar.google.com/scholar_lookup?title=Length+Requirements+for+New+Single-Arc+Unsymmetrical+Vertical+Curve%3a+Crest+Type&author=S.+Easa&publication_year=2008
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/9780309113304
• Authors:
  • Easa, Said M
• Publication Date: 2008

Language

• English

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 38-45
• Monograph Title: Highway Design 2008
• Serial:
  • Transportation Research Record: Journal of the Transportation Research Board
  • Issue Number: 2060
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Highway curves; Highway design; Length; Passing sight distance; Sight distance; Stopping sight distance
• Uncontrolled Terms: Vertical curvature
• Subject Areas: Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01088828
• Record Type: Publication
• ISBN: 9780309113304
• Files: TRIS, TRB
• Created Date: Feb 25 2008 2:36PM