Publication Date:
March 2021

Authors:

Michael Beyer, Conrad Stacey and Arnold Dix

This note summarises what was discovered in a review of the technical background for the change to the critical velocity values resulting from Annex D of (NFPA 502, 2020), as well as the recent developments regarding the critical velocity in Annex D of (NFPA 502, 2020), and why a retraction of this formula is imminent. It is very significant for road tunnel design in many parts of the world.