What is a runway safety area?
Runway safety areas are required by Federal Aviation Administration, and they are a defined surface surrounding each runway that will accommodate airplanes, as well as emergency vehicles, in the unlikely event that an aircraft leaves the runway (such as during an aborted takeoff, for example). The standard runway safety area for commercial service airports, such as Philadelphia International Airport, begins at the end of the runway. It is 1,000 feet long and 500 feet wide.
