In Wikipedia ist eine Liste der jeweiligen Linien wo man die Bedeutung der Buchstaben auf den von dir beschriebenen Tafeln zu sehen ist.
Third Avenue Railway System (TARS)
http://en.wikipedia.org/wiki/Third_Avenue_Railway#LinesLines
Manhattan
The following lines existed in later days:
• 10 Tenth Avenue Line: 42nd Street, 10th Avenue, Broadway, and 125th Street from West 42nd Street Ferry to West 130th Street Ferry
• B Broadway Line: 42nd Street, Broadway, and 125th Street from East 42nd Street Ferry to West 130th Street Ferry
• K Broadway-Kingsbridge Line: East Harlem to the Bronx
• T Third and Amsterdam Avenues Line: Park Row, Bowery, 3rd Avenue, 125th Street, and Amsterdam Avenue from City Hall to Fort George
• X 42nd Street Crosstown Line
• X 59th Street Crosstown Line
• X 125th Street Crosstown Line
The Bronx
The following lines operated in The Bronx. The final streetcar lines were converted to bus operation in 1948.
• A Westchester Avenue
• B Bailey Avenue
• B Boston Road
• C Bronx-Van Cortlandt Park Crosstown
• L St. Anns Avenue
• O Ogden Avenue
• S Sedgwick Avenue
• S Southern Boulevard
• T Tremont Avenue
• U University Avenue
• V Williamsbridge
• W Webster Avenue-White Plains Avenue
• X 138th Street Crosstown
• X 149th Street Crosstown
• X 163rd Street Crosstown
• Z 180th Street Crosstown
Yonkers
The following lines operated in Yonkers, New York:[7] All were converted to bus operation in 1952.
• 1 Broadway-Warburton
• 2 Broadway-Park Ave.
• 3 Broadway
• 4 McLean Ave.
• 5 Nepperhan Ave.
• 6 Tuckahoe Road
• 7 Yonkers Ave.
• 8 Riverdale Ave.
• 9 Elm-Walnut Sts.