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A success story of an innovative concept

Posted: 22 February 2010 | Dr. Walter Casazza, CEO, Karlsruher Verkehrsverbund GmbH (KVV) | No comments yet

In Karlsruhe, a fully developed tram-system has been operating since 1900, and there is also an important railway junction where many main lines and branch lines meet. This situation creates the idea of a track sharing network – connecting the tram and rail network. Using existing infra­structure should help to avoid big investments in new railway or tramlines and a direct connection between the city centre and the countryside makes creating interchanges unnecessary.

In Karlsruhe, a fully developed tram-system has been operating since 1900, and there is also an important railway junction where many main lines and branch lines meet. This situation creates the idea of a track sharing network - connecting the tram and rail network. Using existing infra­structure should help to avoid big investments in new railway or tramlines and a direct connection between the city centre and the countryside makes creating interchanges unnecessary.

In Karlsruhe, a fully developed tram-system has been operating since 1900, and there is also an important railway junction where many main lines and branch lines meet. This situation creates the idea of a track sharing network – connecting the tram and rail network. Using existing infra­structure should help to avoid big investments in new railway or tramlines and a direct connection between the city centre and the countryside makes creating interchanges unnecessary.

The idea is that there is no need for an interchange because the tram simply ‘becomes’ a train. It is hard to imagine that heavy loco­motives and wider EMUs run through a pedestrian precinct and that is why the existing LRVs would need to be modified for heavy rail operation. For this, the Albtal-Verkehrs-Gesellschaft (AVG) developed a ‘dual-mode vehicle’ so that it was ready for production within a federal research project during the 1980s. The study was partly funded by the Federal Ministry of Research and Development; the Federal Railway and the industry gave technical support.

A tramway in the city centre, a railway in the region

The tram-train is designed to be comfortable with both systems for which it has been developed – in terms of power supply, rails and safety.

The tram-train vehicle

Different power supply systems were investigated during the research project. The final decision was made to design the vehicle with a direct current/alternating current (DC/AC) option. In the city of Karlsruhe, the trams run under 750 V DC whilst the German Federal Railway system uses 15 kV (16 2/3 Hz) AC. The dual-mode vehicle is able to sufficiently operate with both modes – 750 V DC within the tram network and 15 kV on the heavy rail system.

A lot of basic conditions were taken into consideration during the construction regardless of the drive system. The tram-train vehicle had to be designed to meet the needs of both the German regulations of tram operation (BOStrab) and the German railway operation regulations (EBO). One issue was the difference in the vehicle width. The maximum width of trams is 2.65 metres, but heavy rail vehicles are often wider than 3 metres. Using retractable steps to bridge the gap between the vehicle and the platform solved this problem. Another difficulty was the geometry of the wheel profile – it had to be designed so that it would fit both the narrow grooved tram rails and heavy rail switches.

To achieve an almost barrier-free access to the vehicles, the Karlsruhe dual-mode LRVs are designed with a ‘middle-floor’ and an access height of 570mm. At standard platforms of this height, level boarding is possible for passengers. At platforms that are 380mm high, passengers have to climb a small step and at platforms that are 760mm high, the retractable step can be lifted up.

Because of the lightweight construction of the tram-train vehicles, the crashworthiness is much lower than for heavy rail vehicles. This fact was compensated by a higher braking performance of the LRVs, which is necessary to operate along streets with car traffic in any case. The issue of passive and active safety is now regulated in a LRV directive of the Eisenbahn-Bundesamt (Federal Railway Authority).

System change-over

Several connections between the existing tram and railway networks were built to link both systems and to allow through running operation. The change between tram and railway operation proceeds automatically at the system change-over. Passengers don’t notice this change of electrical power system and regulations; it is like changing from an A-road to an urban street. The dual-mode LRVs change from the direct current to a short neutral (track) section and finally to alternating current. The section for the system change-over is ideally located on a slight gradient, to allow a vehicle rolling back into a live section if an emergency break stopped it inside the neutral section. If worst comes to worst the neutral section can be supplied with current.

Operation

AVG is owned by the city of Karlsruhe and is a so-called non-state owned railway company (NE-Bahn). AVG operates light-rail services in cooperation with the Verkehrsbetriebe Karlsruhe as the local tram operator, and with the Federal Railway company, Deutsche Bahn AG (DB AG).

The state of Baden-Württemberg is re­sponsible for regional railway services. The Nahver­kehrsgesellschaft as a federal authority orders rail services on the DB network. The tram-train services are handled in the same way as other regional railway services.

The dual-mode LRVs run with a fixed frequency between every hour and every 10 minutes depending on the demand. On the railway tracks, the vehicles reach a speed of 100km/h. On the tramway network, the LRVs running straight into the pedestrian precinct with short stop distances and a maximum speed between 25km/h within the pedestrian precinct, 50km/h on street-running sections and 70km/h on segregated tracks.

Demand

In 1992, the first tram-train line opened from Bretten direct into the city centre of Karlsruhe. The increase in passengers exceeded all forecasts. Shortly after the introduction of the light-rail service, the patronage increased by four times between Bretten and Karlsruhe. Only 2,000 trips per day were made before the tram-train service was established and now 18,000 trips per day are being monitored along this corridor. This result has encouraged local politicians in the region of Karlsruhe to extend the tram-train system in stages.

On all lines where tram-train operation was introduced, a significant increase in patronage were experienced.

Trend

At present, most of the tram and tram-train lines run through the pedestrian precinct of Karlsruhe along Kaiserstrasse. This causes a bottleneck. Now the State Government of Baden-Württemberg has ensured public funding for a light-rail tunnel in Karlsruhe by signing an outline agreement with the City council. By 2016, all trams currently using the pedestrian precinct will travel through a tunnel. The planning phase is completed and the ground-breaking ceremony will take place on 21 January 2010.