INTRO: Saarbrücken is almost ready to emulate Karlsruhe as other cities prepare to marry light and heavy rail technologies. Richard Hope reports from the tracklaying site
GROOVED RAILS have been laid along Kaiserstra§e in the heart of Saarbrücken, and trial running will begin shortly with the first of 28 dual-voltage light rail vehicles built by Bombardier Eurorail at Brugge (RG 12.96 p795). The programme may have slipped a few months, but Dipl-Kfm Norbert Walter, Chairman & Chief Executive of Stadtbahn Saar GmbH (SBS), looks forward to carrying his first fare-paying passengers in the autumn.
Ever since Karlsruhe pioneered the concept of mixing light rail vehicles with main line rolling stock built to different technical standards (DM91 p40), several cities within Germany and a handful elsewhere have been striving to exploit the advantages of through running between existing railways and on-street tramways. This gives LRVs access to fast rail routes segregated from road traffic, but unlike suburban trains, they can also penetrate the city centre, taking commuters and shoppers much closer to their destinations. At any point along a rail corridor, dual-mode LRVs can diverge from existing tracks to reach important traffic generators within a conurbation.
The fact that DB now has five years’ experience of mixing vehicles of lighter construction - which might be perceived as offering lower standards of collision protection - has encouraged imitators. As well as LRVs, it has opened the door to development of a new generation of lightweight low-floor DMUs.
Although Saarbrücken has only 200000 inhabitants, the industrialised Saar region based originally on coal and steel is home to more than 1 million people. The strategy behind the setting up of SBS in 1992 as a dual-mode LRT company was to create an extensive network of light rail routes based mainly on DB’s half-dozen electrified lines which radiate from Saarbrücken, most of which already carry commuter trains.
Walter explains that ’Saarbrücken suffered a 50% decline in public transport use after trams were withdrawn in 1965, reaching a low point in 1982 of 25 million journeys.’ Efforts since then to promote the buses met with success, and 37 million people used them in 1995. However, in that year the principal east - west bus corridor along Bahnhofstra§e was pedestrianised, causing buses to be diverted over the River Saar and back. ’We fear that we will lose traffic in consequence’, says Walter.
To ’regain access to the heart of the city’, and at the same time meet a target set by the city authorities of getting 20% of present car users on to public transport, Walter describes light rail as ’the best answer out of many solutions examined.’ Because of the dispersed nature of the conurbation, ’fast services extending 20 to 30 km from the city are essential’ - hence the need to combine on-street running with existing railways.
As reported in Developing Metros 1995 p62, the first phase approved for construction in October 1994 at a cost of DM540m was to consist of a north - south route 46 km long between Lebach and Sarreguemines, which is just across the border in France. There was also to be a short branch to Schafbrücke. The 28 LRVs on order from Bombardier were required to operate this route.
For the time being cars will operate between Ludwigstra§e, 1 km to the west of Saarbrücken Hauptbahnhof, and Sarreguemines, 19 km away. The initial service planned, requiring 15 cars, will see headways of 5min through the city centre, which will be the first section to be completed; a 30min interval service will run to Sarreguemines. Frequencies will be halved in the evening and at weekends.
This first stage consists of two distinct sections: on-street energised at 750V DC, and existing DB/SNCF tracks at 15 kV 16 2??3Hz. Part of Sarreguemines station is wired for 15 kV, although the SNCF lines are not electrified: diesels will work the two through passenger trains which will continue to run daily between Saarbrücken and Strasbourg.
From Ludwigstra§e to Halbergstra§e (5 km) the tracks are laid along a series of streets but are segregated (except at road intersections) by an 80mm high curb. There are platforms 380mm high and 75m long at each stop, allowing easy entry into a coupled pair of the 37m long cars which have 400mm high floors at the four entrance vestibules. Pedestrians are at liberty to cross the paved tracks to reach the platforms.
Track is double throughout except at the Hauptbahnhof, where four platform tracks are available opposite the main entrance to the station. This is the only place where major civil works have been required in the form of a cut-and-cover tunnel; this carries road traffic so that trams, buses, taxis and pedestrians are free to circulate at street level.
The tracks occupy one side of Kaiserstra§e and subsequent streets, which have been made available to westbound traffic only. The technique used has been to open up one side of the street, carry out service diversions, and then lay the new road structure and surface. After traffic has been diverted on to the rebuilt side of the road, the other side is excavated to lay the concrete slab which carries the rails (above).
On entering Mainzer Stra§e, which is wider as the old city centre is left behind, the trams will occupy a central reservation between two-way traffic flows. All intersections are controlled by traffic lights giving priority to trams.
At Halbergstra§e a short turnback spur passes under the railway bridge carrying the line from Saarbrücken to Sarreguemines; this spur will be extended to Schafbrücke when construction of that branch gets the go-ahead. A ramp takes the trams up to join DB tracks, after negotiating an 80m dead section where the voltage change is made automatically.
SBS to buy DB track
In an unusual move, DB has entered into negotiations with SBS about the possible sale of the line between this junction and the border with SNCF. Negotiations were still continuing in early February.
The railway is a multi-track route with sidings and freight yards. Walter says that DB may be invited to carry out maintenance of the track under contract to SBS. Four new halts will be built, and six existing stations (which are unmanned) will be refurbished.
DB will withdraw its local passenger service when the LRVs take over, but the twice-daily Strasbourg trains will continue to run, along with local freight. Despite this, access to platforms at the new halts will be at track level; existing subways will remain in use at the stations taken over from DB.
DB platform edges are 380mm above rail, and 1600mm from the track centre, whereas the optimum to suit the 2650mm wide cars is 1400mm. The gap is bridged by a folding step extended automatically whenever power is being drawn at 15 kV.
Challenging engineering problem
When the decision to go ahead with the central on-street section was made in October 1993, the cost of the initial 46 km north - south route from Lebach to Sarreguemines was put at DM542m. The federal government agreed in December 1994 to pay DM214m, and in January 1995 the Saarland regional government provided a further DM225m. The other DM103m was to be raised locally by SBS.
However, no work has been done beyond Ludwigstra§e, and there is no firm start date for this section because the funding is not yet assured. SBS now hopes that it will open in 2000.
By far the most serious engineering obstacle to be overcome is the main line leading west from the Hauptbahnhof. This consists of seven widely spaced tracks in a cutting, but an eighth track sweeps over the others on a curved flyover at this point - and all eight tracks are electrified.
Trams face a steep ascent from the temporary terminus at Ludwigstra§e to get above the catenary spanning the flyover track before turning to cross what will be a costly viaduct. Future connections with DB tracks also have to be accommodated at this location, further complicating the design.
Busy Lebacherstra§e, which imposes the maximum gradient of 6% found anywhere between Lebach and Sarreguemines, takes the planned light rail route out of the city and on to a motorway, which it will follow closely on the western side. Diverging to pass through the suburban town of Riegelsberg, the restricted width of the main street requires 2·1 km of single track with two intermediate passing loops. Thus far, a former tram route from Saarbrücken has been broadly followed.
Beyond Riegelsberg, double track is restored as the line swings west to join up near Etzenhofen with the single-track K