Quantitative assessment method for road tunnel fire safety: Development of an evacuation simulation method using CFD-derived smoke behavior

•SE levels were defined and mapped to graphically describe the smoke behavior.•One-dimensional evacuation simulator with various evacuation detection factors was developed.•The evacuation behavior simulation considered visibility by smoke is suggested.•The number of people surrounded by dense smoke was used as an evaluation index.•The proposed method was applied under various inclinations and evacuation scenarios. This study proposes a quantitative method for assessing road tunnel fire safety based on a numerical simulation of in-smoke evacuation. Considering evacuation in tunnels which is a long and large but single and simple space; evacuees are generally in the same space as the fire source but evacuation direction is almost one dimension, a new one-dimensional evacuation simulation was developed wherein the self-determined evacuation necessity detection factors were modeled. Using expedited 1D evacuation simulations, random number results from 2000 simulations determined the mean number of sufferers. To evaluate the influence of smoke on evacuees, various smoke environment (SE) levels were defined as a function of time and longitudinal location using a simplified smoke distribution derived from 3D CFD. The number of people surrounded by thick smoke within 10min of fire ignition was used as an evaluation index for tunnel fire safety. The proposed method was tested under various longitudinal gradients, large heat release rate, and pre-evacuation time scenarios.