The Bureau of Mines, through research and development contracts with the FMC Corp., has developed and tested two automatic fire sensing and suppression systems for large haulage vehicles. This work was undertaken to enhance driver safety, to lessen substantial property damage from fires on large trucks, and to increase the vehicle operator's productivity. One automatic truck fire protection system protects both the engine compartment and brake grid areas, while the second system is used in the engine compartment and fuel tank area. Both systems have redundant fire-sensing capabilities and manual override controls. Upon sensing flames and/or heat, the systems suppress the fire with pressurized, b-c class dry chemical. Both fire protection systems are flexible in design and can be modified for use on other mobile mining equipment. Prototypes of both systems have been subjected to long-term, in-mine validation testing and actual fire tests on 100-ton-capacity trucks at the Pima Mine near Tucson, Arizona, and the erie mine at Hoyt Lakes, Minnesota. During the 4-month endurance test of the first system at pima, an accidental flash fire occured in the test truck while it was working in the pit. The system successfully sensed and automatically extinguished the fire with no injury to the driver and little damage to the truck.