by the Civil Aeronautics Board, Aviation Accident Report: 1945 Page Airways Accident (1945)
“ Close to the edge of the ditch are standard colored conical airport boundary markers, placed about 250 feet apart, which definitely mark the limit of the usable area. They are suitably conspicuous but do not warn of the declivity beyond. Although Captain Decker had flown in and out of National Airport on a number of occasions he testified that he was unaware of the existence of this ditch and stated that he could have prevented the accident had he known it was there. ”
