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.Suppression tests have been carried out varying the type and amount of fire extinguishing agent, the location of the nozzles, and the presence or absence of airflow. In addition, the application rate was varied for dry chemical agents.