Verkehrsbetriebe STI was formed in 1913, with the opening of a tram line between Steffisburg and Oberhofen, which was later extended to Beatenburcht and finally to Interlaken. The operation of trams on the main line (Thun to Interlaken) ceased in 1939, and on the line to Steffisburg in the late 1950s, and since then the STI network has been covered exclusively by buses. At first these were environmentally friendly (and quiet) electric buses, drawing their power from overhead wires, but in the 1970s they switched to conventional, diesel powered buses. STI introduced its first night service in 1993, between Thun and Bern. Further extensions to the network in 1999 and 2001 took STI buses into areas such as Gwatt, which had seen train station closures.