INTRODUCING A SIMPLIFIED APPROACH TO HORIZONTAL CURVE SUPERELEVATION DESIGN - A DISCUSSION OF POTENTIAL ADVANTAGES AND DRAWBACKS

In horizontal curve design, superelevation plays the role of supplementing side friction in order to provide adequate sideways force. Despite being a physical element of geometric design, superelevation has been empirically found to have no significant effect in determining vehicle speed on curves. In contrast, horizontal curve radius is consistently shown to be correlated to 85th percentile speed values measured. Nevertheless, in most geometric design guidelines, which have traditionally been based on the design speed concept, it is implied that, within defined limits, any combination of curve radius and superelevation is acceptable. Usage of a high permissible radius with a low assumed design speed can induce excessive speeds and thus be detrimental to safety. Introduction of the 85th percentile speed as a design parameter in some design standards has provided a useful check on the suitability of design speed. However, the absence in large federal countries (such as the United States and Australia) of a unique nationwide maximum superelevation rate leads to cases where identically-designed curves correspond to different assumed speeds. Proposals for simplifying the relationship between curve radius and superelevation rate are presented in this paper, as potential means for addressing the above issues. The advantages of a simplified approach from both the designer's and road user's viewpoints are identified; potential theoretical and practical drawbacks are also discussed.

• Supplemental Notes:
  • The publisher's German name is Forschungsgesellschaft fur Strassen- und Verkehrswesen (FGSV).
• Corporate Authors:

  Road and Transportation Research Association

  Postbox 50 13 62
  D-50973 Cologne,   Germany 
• Authors:
  • KANELLAIDIS, G
  • Dimitropoulos, I
• Conference:
  • 2nd International Symposium on Highway Geometric Design
  • Location: Mainz, Germany
  • Date: 2000-6-14 to 2000-6-17
• Publication Date: 2000-6

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 641-651

Subject/Index Terms

• TRT Terms: 85th percentile speed; Curvature; Design speed; Geometric design; Highway curves; Highway design; Radius; Superelevation
• Uncontrolled Terms: Horizontal curvature
• Subject Areas: Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00794821
• Record Type: Publication
• Report/Paper Numbers: FGSV 002/67
• Files: TRIS
• Created Date: Jun 28 2000 12:00AM