or sprinkler systems may result in many more deaths and injuries than might occur with such protections. Arson is the setting a fire with intent to cause damage. The definition of arson was originally limited to setting fire to buildings, but was later expanded to include other objects, such as bridges, vehicles, and private property. Some human-induced fires are accidental: failing machinery such as a kitchen stove is a major cause of accidental fires. Hazards caused by transportation Aviation An aviation incident is an occurrence other than an accident, associated with the operation of an aircraft, which affects or could affect the safety of operations, passengers, or pilots. The category of the vehicle can range from a helicopter, an airliner, or a Space Shuttle. Rail The special hazards of traveling by rail include the possibility of a train crash which can result in substantial loss of life. Incidents involving freight traffic generally pose a greater hazardous risk to the environment. Less common hazards include geophysical hazards such as tsunami such as that which struck in 2004 in Sri Lanka when 1,700 people died in the Sri Lanka tsunami-rail disaster. See also the list of train accidents by death toll. Road Traffic collisions are the leading cause of death, and road-based pollution creates a substantial health hazard, especially in major conurbations. Space Space travel presents significant hazards, mostly to the direct participants (astronauts or cosmonauts and ground support personnel), but also carry the potential of disaster to the public at large. Accidents related to space travel have killed 22 astronauts and cosmonauts, and a larger number of people on the ground. Accidents can occur on the ground during launch, preparation, or in flight, due to equipment malfunction or the naturally hostile environment of space itself. An additional risk is posed by (unmanned) low-orbiting satellites whose orbits eventually decay due to friction with the extremely thin atmosphere. If they are large enough, massive pieces traveling at great speed can fall to the Earth before burning up, with the potential to do damage. One of the worst human-piloted space accidents involved the Space Shuttle Challenger which disintegrated in 1986, claiming all seven lives on board. The shuttle disintegrated 73 seconds after taking off from the launch pad in Cape Canaveral, Florida. Another example is the Space Shuttle Columbia, which disintegrated during a landing attempt over Texas in 2003, with a loss of all