with the construction of the new diesel multiple unit IC4, many debaters argue that it is better to electrify major railways and purchase electric multiple units instead, since that is a more common product. At least the route Fredericia-Ålborg must be electrified in order to run electric passenger trains between Jutland and Copenhagen. The route between Kolding-Esbjerg was due to be to open for electric trains in 2015. The government has in 2009 decided to delay all electrification for several years until the new signal system ERTMS is introduced, since electrification earlier than that requires rebuilding of the existing signal system. In September 2013 the government reached a deal with the Danish People's Party and the Red-Green Alliance (Denmark) to use additional oil taxes to create a train fund. This train fund would be used to electrify all of the main line trains by 2025, and increase train speeds to for InterCity trains. This would allow for travel between the cities of Copenhagen, Odense, Esbjerg, Aarhus, and Aalborg in four hours. On 29 May 2015 Banedanmark announced a 2.8 billion DKK (€375 million) contract to have Aarsleff-Siemens electrify 1300 km of tracks before 2026. Safety and signalling Main lines were equipped with the ATC safety system during the 1990s, with a partial, cheaper implementation, ATC train stop, being used on some (but not all) branch lines. A different system, HKT, which was introduced in 1975 and utilises cab signalling, is used on the S-train network, although a simplified version, "forenklet HKT" (F-HKT), is used on some of the lines. Denmark has its own ATC system (ZUB 123), not compatible with other countries. It is a modification of the Swiss system. Trains crossing the border to Sweden or Germany have to have two ATC systems, and handle two electrical supply systems. In order to replace the different and aging signal systems, it has been decided to replace all current signal systems on Banedanmark's active network, except the S-train lines, with ERTMS level 2, relying entirely on cab signalling; general rollout is scheduled for 2018–21. The S-train network is set to be refitted with a suitable urban rail system, possibly a CBTC system allowing driverless trains, by 2020. Safety record Serious incidents on Denmark's railways have been rare. The six most serious are: 1897: The Gentofte train crash. A delayed local train was hit by a special train. 40 were killed and