National Transportation Safety Board (NTSB) Chair Deborah Hersman presides at a meeting on the investigation findings and safety issues of the June 22, 2009 collision of two Washington Metrorail trains, Tuesday, July 27, 2010, at the NTSB in Washington. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

National Transportation Safety Board (NTSB) Chair Deborah Hersman presides at a meeting on the investigation findings and safety issues of the June 22, 2009 collision of two Washington Metrorail trains, Tuesday, July 27, 2010, at the NTSB in Washington. (AP Photo/Charles Dharapak)