A vision is becoming reality!

In September 2002, the citizens of Karlsruhe approved a project solution called ‘Kombi-Lösung’ (‘combined solution’). The term ‘combined’ stands for the two parts of the project – a city light-rail tunnel and a new tram line running parallel to the main pedestrian street in Karlsruhe, on top of a new road tunnel!

The light-rail tunnel

From 2017 there will be a 3.4km-long T-shaped light-rail tunnel running under the main pedestrian street of Karlsruhe – the Kaiserstrasse – with a branch into the south of the marketplace. There will be seven modern, comfortable and safe underground stops and three surface stops. The light-rail tunnel will run under two principal axes of the inner city, both in a west-east direction under the pedestrian area and in a southern junction in a north-south direction under the historical marketplace and which will pass under a four-lane main road.

The underground tracks will be connected to the existing overground network via ramps. The tunnel will link four underground stops on a length of approximately 2.4km in a west-east direction and three stops in a north-south running tunnel section of about 1km-long. The tunnel will consist of a tube approximately 9m in diameter in which two tracks will be laid.

The road tunnel and new tram line

As the capacity of the light-rail tunnel does not suffice to manage the entire road traffic, a new tram line will be constructed on the main road running parallel to the city centre.

Moreover, the new line creates operation flexibility and supports the urban development of the southern parts of the city centre. In addition, the parallel traffic and cross traffic situation for cyclists and pedestrians can be improved without affecting the efficiency of automobile traffic when it comes to inner city development. Therefore, the construction of a 1.6km-long road tunnel is necessary, beginning at an existing underpass in the west and ending after a busy crossroad in the east. In order to maintain the accessibility of the city centre by car, entry and exit ramps are needed at two different places. The car park of a major shopping mall will be accessible via the tunnel. The construction of the road tunnel creates surfaces overground which are required for tram lines and an attractive rearrangement with green spaces. Four rows of trees will be planted on the future main road, giving it a boulevard-like appearance. Three new overground stops are being constructed along the new tram line.

Given the near surface nature of the road tunnel, it needs to be constructed using the cut and cover method by securing the excavation pit. The excavation base will be sealed with a low-lying soft gel base. This prevents a lowering of the groundwater level. Alteration works will be carried out in several construction phases, thus enabling to manage the expected timeand location-related constraints on traffic flow within a reasonable time span. Impacts on traffic have been investigated and considered reasonable in advance by experts.

Why the Kombilösung?

On average, one tram-train every minute runs through the city centre at rush hour and passenger numbers are rapidly increasing. In 1985, 55 million people had travelled with the Karlsruher Verkehrsverbund GmbH (KVV). In 2003 this figure was recorded at approxi – mately 100 million, and in 2010 it reached more than 171 million.

The waiting periods at stops and signal arrangements become longer and longer – Kaiserstrasse is on the border of its loading capacity: tram-train after tram-train. This interferes with people shopping in the city and strolling, and is also a risk especially for older people and children.

For over 40 years now, urban planners, transport services and local politicians have been trying to find solutions that are compatible with the city. The common objective of all these solutions was an improvement of urban planning quality without affecting the accessi – bility of the city centre by an environmentallyfriendly local public transport.

How will the Kombilösung change life in Karlsruhe?

By introducing the Kombilösung solution, the following objectives can be achieved:

● The creation of additional capacities for future developments due to the com – bined solution

● Increase of operational flexibility due to the future second east-western route on Kriegsstrasse

● Release of the urban intersections accompanied by a significant reduction of noise and exhaust emissions

● Rail-free pedestrian area without conflict of utilisation for light-rail traffic and pedestrians

● Development potential in the inner city

● Urban upgrading of the area around Kriegsstrasse and promotion of the inner city development southwards.

A real pedestrian-friendly area will be created in Karlsruhe, allowing people to enjoy undisturbed shopping, walking freely and enjoying drinks under the open sky. The most important issue is that there will be great pleasure for all the people in the city centre – the promenade free of tracks, noise and tram congestion. Also, Kriegsstrasse will get a new face. A train line with grass between tree avenues, with a lot of space for cyclists and pedestrians, with a lot of atmosphere for good sensations for local residents. Thus the Kombilösung will change the atmosphere of life in town.

Will the city of Karlsruhe be a construction area during the next 10 years?

There will not be much interference for local residents, shop owners and pedestrians. For approximately two years, while the subterranean stops are built, there will be a partially open building site. Karlsruhe has experience with building sites of a similar scale, for example, with the rebuilding of the postal gallery or big department stores.

The tunnel will be constructed under – ground via a slurry closed-faced tunnelling machine. The functioning of the machine is presumed to be known. The subsoil is well suited for this method. It mainly consists of gravel and sand. The groundwater level average is at 4-5m below ground level. The tunnel tube is constructed with lining segments of 45cm. The construction of the stops is carried out using the dig-and-cast method. In order to minimise disruption to the environment, specific guidelines were set out concerning planning and implementation: maintenance of light-rail operation, minimisation of disruption for shops and for residents, requirements for construction operations.

What will the underground stops look like?

The underground stops will benefit from light and will be formed very generously. The basis is the newest knowledge of the security interests: a special light draught provides harmonious wall creation, ground creation and cover creation for a pleasant atmosphere. At three underground stops, direct underground access to big department stores will be created. The seven new underground stops are to be placed near the surface, due to predefined construction characteristics of the light-rail tunnel. The depth only amounts to about 11m.

The stops will all dispose of side-boarding platforms, indicating a standard width of 4.5-5.5m depending on passenger volumes and on the respective available space underground.

Considering the fact that modern low-floor tramcars and medium-floor dual mode vehicles will be used on the light-rail tunnel section, platform heights will attain 34cm to 55cm over the top of the rail in order to guarantee accessibility. The platform length of 100m was conceived for a train set in double-traction or for the simultaneous stopping of two individual trains.

Each platform will be made accessible by at least two stairs or escalators. The number and width of the stairs depends on the predicted passenger volume and on the technical requirements for fire protection. Each platform will be provided with at least one lift system to guarantee accessibility. Disabled people can easily use the low-floor vehicles as well as dual mode vehicles without help.

Are subterranean stops less safe or dirtier than surface stops?

The bright stops are equipped with video protection arrangements and the most modern security technology. In contrast to surface stops they will not have to contend with rain, ice or snow. A regular cleaning team will be deployed and all subterranean stops will be non-smoking.

What about money?

Eighty per cent of the activity is financed by the Federal Republic of Germany and the state of Baden-Württemberg. Unfortunately, financing does not include the planning costs. Project promoters have to bear all these costs (about €60 million). The construction of the light-rail tunnel started in January 2010.The current cost level amounts to approximately €680 million. The construction of the road tunnel is planned for 2014.

What is the current status?

Construction work has been progressing well for the last two years. Five of the seven underground stops are already under con – struction. Unfortunately, some delays were caused during the execution of construction work when several walls and unexpected foundation types were found at neighbouring houses in the underground. Furthermore, it became evident that the stipulated construction period of approximately six years represents a major logistical challenge for the company. A one-year extension of the construction period is to be expected.

The target date for putting the light-rail tunnel into service is currently expected to be in 2017. The completion of the overall project is still planned for 2019.

About the author

Dr. Walter Casazza studied at the Technical University of Graz and the Leopold-Franzens-University of Innsbruck. Between 1988 and 1993 he was the Assistant Manager at Innsbrucker Verkehrsbetrieb (IVB) and from 1993 to 2006 he was Vice President and Operations Manager of the Traffic Division of IVB. Since 2006, Dr. Casazza has been the CEO of Albtal-Verkehrs- Gesellschaft mbH (AVG), Verkehrsbetriebe Karlsruhe GmbH (VBK), Karlsruhe Verkehrsverbund (KVV) and Karlsruher Schieneninfrastruktur-Gesellschaft mbH (KASIG).