{"id":"S85110909","label":"Railroads--Automatic train control","description":"","source_url":"https://id.loc.gov/authorities/subjects/sh85110909","normalized_label":"railroads--automatic train control","broader":["http://id.loc.gov/authorities/subjects/sh85110953","http://id.loc.gov/authorities/subjects/sh85111022"],"aliases":["Automatic train control","PTC (Positive train control)","Positive train control","Railroad trains--Automatic train control","Railroads--Automatic speed control","Railroads--Automatic stop"],"source_identifier":"http://id.loc.gov/authorities/subjects/sh85110909","provider":"lcsh","revision":"d5669c0900538da0","taxonomy_revision":"f050b5d4780b1289","title":"Railroads--Automatic train control","url":"/topics/S85110909","kind":"topic-directory","aeo_cohort":"topic-directory","catalogue_revision":"f050b5d4780b1289","numeric_address":"10126423202998649348","address_version":"morton4x16-v1","coordinates":[0,20,19137,62464],"answer_status":"Directory metadata; local answer requires separate source review","truth_status":"Subject descriptor, not a factual answer or a demonstrated knowledge gap","reviewed_answer":null}