Passive RFID tags based on narrow band absorbers are proposed for railway applications. The tags consist of absorbing tiles of size 30 × 30 cm². The de-signs of these narrow band absorbers are presented based on infinite array approximation by using periodic boundary conditions. Then, the radar cross sections (RCS) of finite tiles of these designed absorbers are compared with the corresponding RCS of a conduction plate of the same size of the tiles. The difference between the RCS of the absorbing tiles and the conducting tiles corresponds to the RFID digit “1” or “0”. An experiential verification for a sample of these narrow band absorbers is presented based on measuring a fi-nite tile inside a transverse electromagnetic (TEM) cell. The design of this TEM cell is also discussed in detail.