Critical systems meant to deter a Metrorail disaster failed in the moments before and after one six-car Red Line train rear-ended another at high speed near the Fort Totten station, records and interviews show.

Reams of documents released Tuesday by the National Transportation Safety Board, collected during an eight-month investigation into the June 22 Red Line crash that killed nine, bear out Metro’s struggle to maintain its infrastructure, from complex electronic signaling equipment to simple radios.