Simplified Approach for Assessing Initial Fire Development and Spread in Passenger Rail Vehicles

Whether a fire in a passenger rail vehicle remains small or grows to encompass the vehicle and how large the fire may become largely depend on the initiation fire, vehicle interior lining materials and contents, vehicle configuration, and ventilation. Assuming fixed configuration and ventilation, the initiation fire, interior materials, and contents are critical variables. Evaluation of the fire hazards represented by different interior lining materials when exposed to various initiation fire scenarios can be costly and time-consuming with full-scale fire tests. However, small-scale fire tests are less expensive, and numerous tests can be performed in a short time. Small-scale test data coupled with initiation fire data and computational modeling can be used to cost-effectively assess a wide range of scenarios and material combinations for existing and proposed vehicle designs. This paper proposes a simplified approach for characterizing initiation fires and predicting the potential for flame spread on the basis of data that can be obtained from small-scale fire tests. Through the application of a simple screening tool, it is possible to quickly assess a material's propensity to spread flames over a range of initiation fires. This approach can be used to support threat, risk, and vulnerability assessments of existing rail stock and to screen materials for new vehicle design. In conjunction with additional assessment of initial flame spread characteristics, the screening tool can be used with computational fluid dynamics fire-modeling tools to predict the overall development and spread hazard of the fire for specific vehicle configurations and resultant infrastructure impacts.