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Distinctly different fire hazards exist within the engine compartment of a transit vehicle and various detection methodologies may be employed to detect fire events arising from these hazards. The engine compartment presents a particularly challenging environment and it is important to select the correct methodology to ensure timely detection response in the early stages of the development of a fire whilst minimizing nuisance alarms. The choice of the correct detection methodology for a specific fire hazard is therefore determined by the suitability of the methodology for the detection of the anticipated fire event within the environment in which it is required to operate. This paper presents experimental data to demonstrate the variation in the response times of different detection methodologies in the presence of common fire events in the form of simulated flaming fuel fires and a simulated electrical fault in the form of an overheated electrical cable.

Few standard approval tests exist for fire extinguishing systems for commercial vehicles, such as transit vehicles, coaches etc. Therefore, a representative test article has been constructed to evaluate the fire extinguishing performance of current in-house fire protection systems. This data will then be used as a benchmark against which the performance of future fire extinguishing systems can be judged. The test article is a fire-hardened simulation of a rear-engine transit bus. Several fire locations are used, in two configurations: “small” and “large”. The former encompasses diesel fuel spray fires and small, obscured diesel pool fires some containing additional wood chips; the latter represents a more developed diesel fuel spray and larger diesel pool fires. Tests have also been run simulating the ignition of a diesel fuel spray impinging on a hot turbocharger. Parameters pertaining to restrike have also been investigated.