into a major street. Burning fuel set fire to a tramcar. All 20 people aboard the plane and 32 passengers of the tram died. In some areas, an aircraft's fuel tank is also referred to as an aircraft fuel cell. Water supply Water supply systems can have primary or backup power supplied by diesel-fueled generators fed by a small "day tank" and a much larger bulk storage fuel tank. Safety Proper design and construction of a fuel tank play a major role in the safety of the system of which the tank is a part. In most cases intact fuel tanks are very safe, as the tank is full of fuel vapour/air mixture that is well above the flammability limits, and thus cannot burn even if an ignition source were present (which is rare). Bunded oil tanks are used for safely storing domestic heating oil and other hazardous materials. Bunding is often required by insurance companies, rather than single skinned oil storage tanks. Several systems, such as BattleJacket and rubber bladders, have been developed and deployed for use in protecting (from explosion caused by enemy fire) the fuel tanks of military vehicles in conflict zones. For stationary fuel tanks, an economical way to protect them from hazards like extremes of temperature and vehicle crashes is to bury them. However, buried tanks are difficult to monitor for leaks. This has led to concern about environmental hazards of underground storage tanks. See also Electrification Explosion Fast fuel system Fuel container Fuel filter Fuel leak Fuel line Fuel pump Jettison Fuel bladder References External links Reduction of Fuel Tank Flammability in Transport Category Airplanes (U.S. Environmental Protection Agency). Fuel tank harmonization (Aviation Rulemaking Advisory Committee) U.S. Unveils New Rule On Airplane Fuel Tanks, by United States Department of Transportation. 2005 Ford GT Powertrain Vehicle technology Fuel containers