DM 24,000,000 (€12,270,000), of which 75% was funded by the German Federal Government, 20% by the state of North Rhine-Westphalia and 5% by the city of Dortmund. The longest span between support pillars is 38.5 metres (126.3 ft), where it crosses the university road, which bisects the two campuses. Just beyond the road the H-Bahn crosses through a nature reserve at its maximum elevation of about 16 metres (approx. 50 feet) above ground. In order to prevent passengers getting close to the track at stations, there are platform edge doors between the platform and the track. As soon as the vehicles arrive in the station, doors in the partition open automatically, along with the train car doors. In 1993, following a three-year construction period, a new 900 m (0.56 mile) long branch was opened, along with two new stations, one in Eichlinghofen and another at the S-Bahn station at Dortmund university. This construction included technology considered to be the first of its kind in Germany. The existing system was renovated, and equipped with technology which allowed determining the train's location with a much higher precision — within 3 cm (1.2 in). These changes allowed for a higher speed, and trains can now also follow each other more closely. Three new carriages were supplied by Siemens. An extension into the nearby technology park was opened on 19 December 2003, which means the current network, including this final extension, has a length of 3.162 km (approx. 2 miles). The building of this section cost around €15,500,000. Line 1 operates between the Technology Park and Eichlinghofen, and during the day carriages arrive every ten minutes, stopping at the university and the S-Bahn stop, where there is a connection every twenty minutes to Dortmund city centre, and Bochum. Two trains serve line 1. Line 2 is the original line between the North and South campuses of the university, and is served by a third train. A reserve fourth vehicle is available, and there is also a maintenance vehicle. Further extensions to the H-Bahn network were being considered, but were not cost-effective enough: Between the university and the central bus and train station of Dortmund. Eastward from the university, as far as to the Märkische Strasse, southeast of downtown Dortmund. Düsseldorf Airport A nearly identical monorail system called SkyTrain transfers passengers at Düsseldorf Airport, which opened on 1 July 2002 after almost six years of