Magic numbers in tunnel fire safety

In this paper we discuss the phrase magic numbers in tunnel fire safety. There is nothing magical about the numbers, but it is magical how they are derived. Sometimes it is even a mystery. A magic number is defined here as a technical design value obtained from a round table discussion of experts without any direct physical validation or traceable origin. They may be based on long experience and some limited experimental data but these numbers are usually a consensus in a group of experts sitting in technical meetings. They also tend to be interpreted as true values in the design process and they tend to live their own lives after assignment. Numerous design values that can be regarded as a magic number according to the above definition are analysed and discussed in this paper. Examples of such design values are the choice of heat release rates in MW, the distance in metres between escape routes and the choice of time-temperature curves. Today's guidelines include various magic numbers and in order to avoid too many prescriptive solutions we need to deal with the problem based on rational engineering solutions, i.e. go from a prescriptive designing towards a performance based designing using results from risk analysis and new research. A way to do this is discussed in the paper (A). For the covering abstract of the conference se ITRD E216860.


  • English

Media Info

  • Pagination: pp21-27
  • Monograph Title: Proceedings from the Third International Symposium on Tunnel Safety and Security, Stockholm, Sweden, March 12-14 2008
  • Serial:
    • Issue Number: 2008:11
    • Publisher: SP Sveriges provnings- och forskningsinstitut, Sweden
    • ISSN: 0284-5172

Subject/Index Terms

Filing Info

  • Accession Number: 01141059
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • ISBN: 978-91-85829-25-5
  • Files: ITRD
  • Created Date: Sep 30 2009 8:58AM