be converted to ETCS Level 2 by 2030. The ZUB 123 system is however not used on the Copenhagen S-train network, where another, incompatible safety system called HKT (da:Hastighedskontrol og togstop) has been in use since 1975, as well as on the Hornbæk Line, which uses a much more simplified ATP system introduced in 2000. This system is gradually being replaced by the modern and worldwide CBTC signalling standard as of 2022. Norway Bane NOR—the Norwegian government's agency for railway infrastructure—uses the Swedish system of ATC. Trains can therefore generally cross the border without being specially modified. However, unlike in Sweden, the ATC system used in Norway differentiates between partial ATC (delvis ATC, DATC), which ensures that a train stops whenever a red signal is passed, and full ATC (FATC), which, in addition to preventing overshooting red signals, also ensures that a train does not exceed its maximum allowed speed limit. A railway line in Norway can have either DATC or FATC installed, but not both at the same time. ATC was first trialled in Norway in 1979, after the Tretten train disaster, caused by a signal passed at danger (SPAD), occurred four years earlier. DATC was first implemented on the section Oslo S - Dombås - Trondheim - Grong between 1983 and 1994, and FATC was first implemented on the Ofoten Line in 1993. The high-speed Gardermoen Line has had FATC since its opening in 1998. After the Åsta accident occurred in 2000, the implementation of DATC on the Røros Line was accelerated, and it became operational in 2001. Sweden In Sweden the development of ATC started in the 1960s (ATC-1), and was formally introduced in the early-1980s together with high-speed trains (ATC-2/Ansaldo L10000). As of 2008, 9,831 km out of the 11,904 km of track maintained by Swedish Transport Administration—the Swedish agency responsible for railway infrastructure—had ATC-2 installed. However, since ATC-2 is generally incompatible with ERTMS/ETCS (as in the case of the Bothnia Line which is the first railway line in Sweden to exclusively use ERTMS/ETCS), and with the aim of Trafikverket to eventually replace ATC-2 with ERTMS/ETCS over the next few decades, a Special Transmission Module (STM) has been developed to automatically switch between ATC-2 and ERTMS/ETCS. United Kingdom In 1906, the Great Western Railway in the UK developed a system known as "automatic train control". In modern terminology, GWR ATC is classified as an automatic warning