The U. S. Army Tank Automotive Research, Development and Engineering Center (TARDEC) National Automotive Center (NAC) owns a fleet of ten Hydrogen Hybrid Internal Combustion Engine (H2ICE) vehicles that have been demonstrated in various climates from 2008 through 2010. This included demonstrations in Michigan, Georgia, California and Hawaii. The fleet was consolidated into a single location between July 2009 and April 2010. Between July of 2009 and January of 2011, data collection was completed on the fleet of H2ICE vehicles deployed to Oahu, Hawaii for long-term duration testing.The operation of the H2ICE vehicles in Hawaii utilized standard operation of a non-tactical vehicle at a real-world military installation. The vehicles were fitted with data acquisition equipment to record the operation and performance of the H2ICE vehicles; maintenance and repair data was also recorded for the fleet of vehicles. Over the year-long demonstration, the vehicles were driven by a wide range of military services including the Army, Air Force, Navy, Pacific Command (PACOM) and National Guard; each service had different drive cycles. Drivers were trained in the operation of the H2ICE vehicles and the safe use of hydrogen, and were surveyed to solicit their feedback on the H2ICE vehicles.The demonstration of this fleet of H2ICEs identified maintenance issues associated with long term operation of the vehicles, as well as user concerns that would need to be addressed if hydrogen vehicles are going to be transitioned from research and development fleets to general commercial use vehicles. Vehicle performance data collected showed the fuel efficiency of the fleet of vehicles and the vehicle's reliability.