 Nicknamed City Cars, the R1s were the first of five subway car classes collectively referred to as Arnines, or R1-9s, with future passenger stock orders – including contracts R4, R6, R7/A, and R9 – being virtually identical, with minor mechanical and cosmetic variations.The first R1s were delivered in 1931, in anticipation for the opening of the IND Eighth Avenue Line.For their time, the R1s introduced several improvements to subway car design that greatly sped up the flow of passengers in and out of trains.