In transportation, hydrail is the generic term describing all forms of rail vehicles, large or small, which use on-board hydrogen fuel as a source of energy to power the traction motors, or the auxiliaries, or both. Hydrail vehicles use the chemical energy of hydrogen for propulsion, either by burning hydrogen in a hydrogen internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to run electric motors. Widespread use of hydrogen for fueling rail transportation is a basic element of the proposed hydrogen economy. The term has been used by research scholars and technicians around the world. Hydrail vehicles are usually hybrid vehicles with renewable energy storage, such as batteries or super capacitors, for regenerative braking, improving efficiency and lowering the amount of hydrogen storage required. Potential hydrail applications include all types of rail transport: commuter rail; passenger rail; freight rail; light rail; rail rapid transit; mine railways; industrial railway systems; trams; and special rail rides at parks and museums. The term hydrail is believed to date back to 22 August 2003, from an invited presentation at the US Department of Transportation's Volpe Transportations Systems Center in Cambridge, MA. There, Stan Thompson, a former futurist and strategic planner at US telecoms company AT&T gave a presentation entitled the Mooresville Hydrail Initiative. However, according to authors Stan Thompson and Jim Bowman, the term first appeared in print on 17 February 2004 in the International Journal of Hydrogen Energy as a search engine target word to enable scholars and technicians around the world working in the hydrogen rail area to more easily publish and locate all work produced within the discipline. Since 2005, annual International Hydrail Conferences have been held.