This paper summarises a series of large-scale fire suppression tests conducted to simulate a fire in the trailer of a heavy goods freight truck on a roll-on roll-off (ro-ro) cargo deck. The tests were conducted with a traditional deluge water spray system as well as a deluge high-pressure water mist system. Parameters such as the water discharge density, the system operating pressure, the nozzle K-factor and whether the fire was fully exposed to the water spray or shielded were varied. The total and convective heat release rate of the fire was measured in order to determine the fire suppression and fire control capabilities of the tested systems. Test results indicate that a water discharge density of at least 10 mm/min is necessary to provide fire suppression of a fire in a heavy goods freight truck, whilst 5 mm/min would provide fire control. Furthermore, the test results indicate that a high-pressure water mist system would require higher flow rates as compared to a traditional water spray system in order to provide fire control.