The SRT Dark Red Line, or Thani Ratthaya Line (Thai: รถไฟชานเมือง สายธานีรัถยา) is part of the SRT Red Line suburban railway system to serve the greater Bangkok Metropolitan Region running for 26 km between Bang Sue Grand Station and Rangsit. When fully completed, the line will run on a north–south axis through Bangkok, from Thammasat University's Rangsit campus in Pathum Thani Province to Maha Chai in Samut Sakhon Province for a full length of nearly 87 km.