The Technical Committee on Road Tunnel Operation (C3.3) of the World Road Association (PIARC) and the International Tunnelling Association (ITA) set up a joint initiative to improve the fire resistance of road tunnels. The role of PIARC was to define the objectives of resistance to fire of road tunnel structures. ITA's role was to develop construction techniques and materials to meet these objectives. The basic design criterion to be met by any tunnel structure was that there should not be any risk of progressive collapse. Proposed design guidelines developed by Working Group No. 6 'Fire and Smoke control' of the PIARC Technical Committee on Road Tunnel Operation are presented. The PIARC design criteria are based on existing temperature-time curves. It has been proposed that tunnel fire curves should be introduced into European and international standards.
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