Probabilistic design fire scenarios for performance-based design involving passenger vehicles

Existing design guidance indicates a peak heat release rate (HRR) of 5-8 MW for a single passenger vehicle or 15 MW for multiple vehicles. However, these recommendations are based on data from older vehicles which do not reflect modern trends in construction and consumer preferences. This work presents data from 9 additional fire tests of modern passenger vehicles recently conducted by the authors. These data are used to improve the validation basis of a model for the HRR of passenger vehicles. The model is then used to develop probabilistic design fires for the most challenging but realistic fire scenario for passenger vehicles based on their size. Data on vehicle sales are used to develop distributions on the size of vehicles. These distributions are then used with the model to evaluate distributions for the HRR and total heat released for the population of vehicles on the market. The analysis showed that greater HRRs of 10-16 MW are more representative of the hazard posed by modern vehicles. A solid flame heat transfer model, and a flux-time product ignition model, are used to evaluate the likelihood that a single vehicle fire will transition to a multiple vehicle fire. • The size of modern vehicles has increased year over year since the 1970s. • Larger vehicle fires produce greater peak HRRs and flux-time products. • Peak HRRs of modern vehicle fires are significantly greater than existing design guidance. • Ignition of adjacent vehicles is more likely with modern vehicle fires.