SAFETY IN GEOMETRIC DESIGN STANDARDS II: RIFT, ROOTS AND REFORM

Many believe that roads built to geometric design standards are safe. The truth is that the safety of such roads is largely unpremeditated. This central claim is substantiated in detail. The roots of the rift between belief and reality seems to be in two: first, the tendency to define failure not by crash frequency and severity but by surrogates such as deficient sight distance, insufficient centripetal force, etc.; and second, the inclination to deal with the road user as with inanimate matter that has properties akin to physical constants. Both may be linked to the tribal custom of civil engineers. The last part of the paper explores avenues for reform. Designers of roads believe that roads built to standards are safe. Lawyers and judges assume that roads designed to standards are appropriately safe. Beliefs, no matter how passionately held, and assumptions, no matter how repeatedly applied, are fallible guides to truth. The truth is that roads designed to standards are not safe, not unsafe, and not appropriately safe; roads designed to standards have an unpremeditated level of safety. This is the claim to be substantiated. In the first part of this paper the author attempts to provide a systematic basis for the claim. A sequence of arguments is used to show that if the safety of a road is measured in terms of crash frequency and severity, then statements about roads built to standards being as safe as they can be, or as safe as they should be are untenable. One of the arguments used (and substantiated in the companion paper) is that standards tend to be written not with crashes but with crash surrogates in mind. Sight distance, separation between oncoming vehicles, centripetal force and driver comfort are substitutes for safety (as measured by crash frequency and severity). Because the relationship between surrogates and safety is uncertain and often counter-intuitive, there is no clear link between geometric design standards and safety. In the second part of this paper the author examines the historical root of the design paradigm that allowed the rift between crashes and surrogates to develop and caused the separation between intent and reality. The last part of the paper examines options for reforming road design; what to do so that the roads we build are appropriately safe.

  • 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:
    • Hauer, E
  • Conference:
  • Publication Date: 2000-6

Language

  • English

Media Info

  • Features: References;
  • Pagination: p. 24-35

Subject/Index Terms

Filing Info

  • Accession Number: 00794764
  • Record Type: Publication
  • Report/Paper Numbers: FGSV 002/67
  • Files: TRIS
  • Created Date: Jun 23 2000 12:00AM