Superelevation design for sharp horizontal curves on steep grades

Darren J. Torbic, Eric T. Donnell, Sean N. Brennan, Alexander Brown, Mitchell K. O'Laughlin, Karin M. Bauer

Research output: Chapter in Book/Report/Conference proceedingChapter

23 Scopus citations


The objective of this study was to develop superelevation criteria for sharp horizontal curves on steep grades. Field studies were undertaken and vehicle dynamics simulations (point mass, bicycle, and multibody) were performed to investigate combinations of horizontal curve and vertical grade design criteria. The vehicle dynamics simulations used AASHTO design criteria and field-measured data to investigate the safety margins against skidding and rollover for several vehicle types on sharp horizontal curves with steep grades. Research results indicated that for a simple horizontal curve, the maximum rate of superelevation should not exceed 12% on a downgrade. A spiral curve transition is recommended if the maximum superelevation rate is greater than 12%. On upgrades of 4% and greater, the maximum superelevation rate should be limited to 9% for minimum-radius curves under certain conditions. The superelevation attained at the point of curve entry should be checked and compared with a lateral friction margin condition so that the lateral friction margin on curve entry is not less than the margin within the curve. On multilane highways, the "Stay in Lane" sign should be installed in advance of sharp horizontal curves on steep downgrades.

Original languageEnglish (US)
Title of host publicationTransportation Research Record
PublisherNational Research Council
Number of pages11
ISBN (Electronic)9780309295345
StatePublished - 2014

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Mechanical Engineering


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