Design speed is one of the principal parameters for the design of road alignment, but the operating speed is the effective velocity that drivers adopt in relation to the conditions dictated by the characteristics of the road, its environment, and the vehicle. The difference between the design speed and the actual operating speed, if it occurs where alignment is inconsistent with the operating speed, can determine the nature and extent of hazards for safe driving. It is possible to identify three distinct conditions on highway links that can be considered detrimental to road safety: (I) where operating speed is greater than the design speed; (II) where there are different speeds on contiguous lengths; and (III) where the side friction needed in curves is less than that available. A survey of actual speeds and road accidents was conducted on specific sections of rural two lane Sicilian highways with such alignment inconsistencies. The comparison between the degree of safety defined according to the criteria found in literature, and road accident data over the last seven years, has enabled the design classes of these criteria to be modified in order to match the local (Italian) conditions of speed and pavement skid resistance. On the basis of these adjustments a better correlation between alignment inconsistency and road hazard was found.

  • 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:
    • Cafiso, S
  • Conference:
  • Publication Date: 2000-6


  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 377-387

Subject/Index Terms

Filing Info

  • Accession Number: 00794793
  • Record Type: Publication
  • Report/Paper Numbers: FGSV 002/67
  • Files: TRIS
  • Created Date: Jun 27 2000 12:00AM