Case Studies: Tram-Train “Kombilösung”, Karlsruhe, Germany

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Project Overview
Figure 1: “Kombilösung” Karlsruhe, Germany
Tram-Train “Kombilösung” Karlsruhe, Germany
Project Type: Both
Type of Project Financing: Public
Contract duration: 10 years
Budget: €897,324,000 (2014)
Project Time Line
1970s: Initial thoughts about tunnel.
1990: Resolution in the municipal council for a tram-train tunnel in “Kaiserstrasse”
1996: First (failed) referendum
2002: Second referendum to decide over construction of the “Kombilösung” with a positive result of 55.55 % pro-“Kombilösung” votes
2003: Formation of KASIG mbH as principal of the “Kombilösung”
2004: Appropriation request through the Municipal Transport Financing Law of the state of Baden-Württemberg
2005: “Planfeststellungsverfahren” (Planning Approval Procedure) for the partial project “Kaiserstrasse”, as well as the development of a development plan for “Kriegsstrasse”
2008: Approval under building law for the plans of the “Kombilösung” and approval for financing through the GVFG program. Decision to first build the tram-train tunnel in “Kaiserstrasse” and financial agreement between the state of Baden-Württemberg and the city of Karlsruhe to implement the “Kombilösung”
2009: Invitation to tender
2010: Beginning of construction works in “Kaiserstrasse”
2015: Beginning of construction works in “Kriegsstrasse”
2018: Planned opening of the tram-train tunnel
2019: Completion of construction works in “Kriegsstrasse”


The “Kombilösung” Karlsruhe is an innovative public transport infrastructure project with the aim of creating space for increased mobility and quality of life in the city centre of Karlsruhe. The city of Karlsruhe is located in the south-west of Germany. It is the second largest city in the German Federal State of Baden-Württemberg with a population of around 300,000 people. The infrastructure project mainly concerns the inner-city region.

The project consists of two parts which are linked by a joint connection, as shown in Figure 2. Both parts are deemed necessary in order to fulfil the project’s goals.

One part of the project is a tram-train tunnel in the street ”Kaiserstrasse” including a branch line in the southern direction from the tram-train stop “Marktplatz” (market place) to the stop “Augartenstrasse”. The stop “Marktplatz” is the main junction between the east-west tram-train tracks and the north-south tracks, which connect the inner city with Karlsruhe’s main station. “Kaiserstrasse” is a pedestrian area and the main shopping area with several shops, restaurants and cafes, located in the city centre. However, the pedestrian area is shared between the tram-trains and pedestrians. Therefore, both, the flow of the tram traffic and the pedestrians are disturbed.

The tram-train tunnel in “Kaiserstrasse” (east-west direction) is 2.4 kilometres long and includes four underground stops. The branch in the north-south direction is one kilometre long and includes another three underground stops. Several ramps are built to connect the underground tracks with the tracks above ground. All of the underground stops are approximately 13 meters deep, except for one which is only 7 meters deep. The tunnel itself is built as one tube with an outer diameter of 9 meters (inner diameter: 8.2 meters) with one track going in each direction.

The second part of the “Kombilösung” includes an additional tram-train track in the “Kriegsstrasse” street with extensive green areas, as well as cycle paths. The vehicle traffic currently managed on “Kriegsstrasse” is lead through a second tunnel that underpasses the newly built tram-train tracks on “Kriegsstrasse”.


Figure 2: Mapofthetunnels in “Kaiserstrasse” (red) and Kriegsstrasse (green); an interactive map can be found on the official project homepage

The car tunnel in “Kriegsstrasse” is designed at 1.6 kilometres long and will replace the current busy road, which at the moment includes several underpasses for “fast-track” traffic. The tunnel starts at the stop “Karlstor” at the western end and ends at the node “Ostendstrasse” in the street “Ludwig-Erhard-Allee”. The tracks in “Kriegsstrasse” are an additional load relief for the tram-trains going through “Kaiserstrasse”. There will be three further stops for this line. Between “Karlstor” and the “Mendelssohnplatz” stop, a pedestrian boulevard framed by trees and green areas with wide cycle paths and walkways is also incorporated, besides the new tram-train tracks. With this boulevard, the city centre is stretched out from “Kaiserstrasse” to “Kriegsstrasse”. This constitutes the beginning of a long needed southwards stretch of the centre.

The project is currently still under construction and planned to be finished in 2019. Although the project has only been realized in the last few years, the idea for a tunnel in “Kaiserstrasse” exists since the 1970s. The idea has constantly been developed and has been made public in 1990 with a resolution in the municipal council for the tunnel. A first referendum in 1996, however, has been negative. In 2002, a second referendum voted for the joint project as it is executed now.

The Contracting Authority (Public Party)

The Karlsruher Schieneninfrastruktur-Gesellschaft mbH (KASIG) is the principal for the project. The company was founded in 2003, solely for the construction of the “Kombilösung”. It is owned 100% by the “Karlsruher Versorgungs-, Verkehrs- und Hafen GmbH“(KVVH), which is again owned 100% by the city of Karlsruhe. KVVH incorporates all of the city’s transportation and public utilities companies, as well as the inland port of Karlsruhe.

Since the KASIG mbH is indirectly owned by the city of Karlsruhe, it can be assumed the project is driven locally with the purpose of reorganizing the traffic in the city of Karlsruhe in order to free the centre from congestion and to provide fast, reliable and better connected public transport in Karlsruhe.

Sources of Financing

As of the Municipal Transport Financing Law (GVFG), the project is funded through public subsidies by 80%. The remaining 20% are borne by the KASIG mbH. This, however, does not accurately match the latest numbers that have been made public in December, 2014 (see Table 1).

The financing structure is as follows:

The 80% of public financing is divided between the Federal Government of Germany that provides 60 % of the funding through the Municipal Transport Financing Law (GVFG), and the State of Baden-Württemberg that provides 20% of the funding, also through the GVFG.

As of 2014, the subsidies by the Federal Government came to €426.7 million and the subsidies of the State to €142.2 million. In order to complete the project, €897.3 million are needed. The remaining €328.4 million are provided by the KASIG mbH.

Table 1: Summary of the financing structure for the “Kombilösung”

Overall budget Subsidies of the Federal Government (Germany) Subsidies of the State Government (Baden-Württemberg) KASIG mbH
897.3 Mio € 426.7 Mio € (48%) 142.2 Mio € (16%) 324.4 Mio € (36%)


Users directly benefiting from the project are the public transport users living in Karlsruhe or the surrounding areas, as well as residents along the main construction areas ("Kriegsstraße" and "Kaiserstrasse"). Residents of and visitors to Karlsruhe will benefit from a car and tram-freed pedestrian area in the city centre and a less dissected district around the "Kriegsstrasse". Thus, the infrastructure project is basically a city development project.

Other parties that yield benefits are shopping, food and other service businesses along the pedestrian area "Kaiserstraße", as well as businesses located along the newly emerging southward stretch of the city centre in the “Karl-Friedrich-Strasse” street .These businesses will profit by the upgraded and then traffic-freed pedestrian area, whereby an improved shopping experience for customers could be provided.

Public transport operators will benefit from the modern infrastructure that enables a high-quality service and fast connections.

Overall, the city of Karlsruhe will provide a more attractive environment for residents and visitors alike.

Key Purpose for Public Financing Model Selection

It is assumed that a PPP model was rejected because public interest rates are extraordinarily low in Germany, compared to private interest rates.

Project Locality and Market Geography

The tram-train tunnel in “Kaiserstrasse” and the car tunnel in “Kriegsstrasse” are both located in the city centre and are built with the purpose of ensuring traffic flow in the inner city. Therefore, the project is classified as urban.

Procurement & Contractual Structure


The company commissioned for the construction works has been selected through a tender process, which is a standard procedure for projects similar to the “Kombilösung”. Since the project consists of two separate parts, there is a separate tender process for each.

The tender process for the tram-train tunnel in “Kaiserstrasse” has started in 2009. The tender documents have been sent to five chosen consortia on June 19, 2009. The proposals had to be handed in by October 6, 2009. In the first quarter of 2010, the results had been published. On February 23, 2010, KASIG has announced the company with the winning bid and the cost for the carcass works. The company responsible for the works is Alpine Bau Deutschland AG.

The construction tender in “Kriegsstrasse” was handled similarly, but started only in 2014. After prequalification, six associations have been approved for the tender process, to which the documents had been sent on November 28, 2014. The deadline for the application was March 26, 2015. There is no further information available at this time (2015), since the tender process is not yet completed.

Risk Allocation

There is no information available on the risk management of the project. It can only be assumed based on the structure of the project (see Figure 3). All risks are totally public, since it is a public project. Commercial, financial and regulatory risks are all moderate to acceptable (since they do not apply to the project), therefore no risk mitigation strategies are needed.

Figure 3: Risk allocation


Since the project is not yet completed, no conclusions on the eventual performance can be drawn at the moment. However, the project is well underway, with no substantial delays and it can be expected that the project will achieve its goals.

Nevertheless, there have been delays that have been caught up with, in the course of the project.

The construction of the underground stops of the tunnel in "Kaiserstrasse" has been delayed up to 12 months. This was caused by a fault in resource and space planning. There have not been enough construction workers working at the respective sites. Additionally, the construction sites were designed as too small in the planning phase in 2004. Obstacles in the building ground were regularly found that needed to be removed and in some building excavations several pumpings were needed to ensure tightness, which all caused unplanned work stops.

The insolvency of the main construction company, Alpine Bau Deutschland AG in 2013 was also highly discussed. However, the city claims that this has caused a delay of only two days.

Despite the above, with the closure of the street “Kaiserstrasse” between the stops “Kronenplatz” and “Marktplatz” in 2013, 15 months of building time have been regained. Therefore, the project is now said to be more or less within schedule.

There has been a substantial cost increase of around 50% due to the increase in costs for the construction works and administration. The increase in construction costs resulted from additional or modified services, as well as additional amounts in the range of civil engineering works and increased demands on quality assurance. Moreover, the construction of interim arrangements for tram, road and pedestrian traffic were required and new sewage pipes had to be installed. The site clearing, in particular the investigation and disposal of ammunition and dud bombs left over in the building ground after the Second World War, added more unforeseen costs. The additional budget for administrative matters can be broken down into project controlling, construction supervision and site management, as well as costs for experts and testing engineers for geotechnics and tunnel construction and legal matters.

Project Outcomes

The project is still under construction; therefore, no statements regarding project outcomes can be made.