Cabintaxi PRT System

Cabintaxi video now available on YouTube

view of cabintaxi
test track

Cabintaxi, a joint venture of Messerschmitt-Bolkow-Blohm (MBB) and Demag, has been the only group in the world to build a small-vehicle PRT system (referred to by some as a "true" PRT). A large test track facility was built in Hagen, Germany, that was used for an extensive testing program conducted from 1973 to 1979. 

The Cabintaxi technology logged over 400,000 miles of vehicle testing and operations from 1975 to 1978. In 1977 the system completed fleet operation endurance testing of 7,500 continuous vehicle hours, and again in 1978, of 10,000 continuous vehicle hours, for a total of 17,500 vehicle hours of fleet endurance testing. The fleet was made up at its maximum in this time period, of 24 operating vehicles over two levels. The Cabintaxi endurance tests are the only fleet endurance test of this scale ever carried out successfully, including tests with vehicle separations under 3 seconds.

The cost of this extensive development and testing work in 2012 dollars has been estimated to be about $300 million. It has also been estimated that an updated version (hardware,  software and necessary testing) of this technology could be accomplished for about $10 million at this time within a three year period (faster is more funds were provided). All necessary technical drawings and test procedure documents are currently held by the Cabintaxi Corporation, located in Detroit. It represents a truly amazing investment opportunity at this time.

The German Government considered this PRT development effort successfully completed and ready for urban deployment , but a planned application in Hamburg was terminated for budgetary reasons in 1979. With the termination of the Hamburg project, the participating companies withdrew from the field.

No other PRT concept has been able to match Cabintaxi's level of development during the past 30+ years. However, the Raytheon Company recently (1996) opened a PRT 2000 test track in Marlborough, Massachusetts and it represented a second effort to develop a deployable PRT technology. But, the Raytheon PRT 2000 program was cancelled in 1999 as part of a company-wide budget-cutting action. 

Cabintaxi was, and still is, unique in that its vehicles ride on top of the guideway as well as running suspended underneath the guideway. This was done to provide for two-way access on a single guideway to all stations in the system to reduce significantly the total miles of elevated structure (the most costly part of the system) within a large urban network. A diagram is provided that illustrates this idea more completely. Extensive studies of this issue were made and the least costly alternative turned out to be the over&under solution, shown above.

In 1969, Demag and MBB, separately, started design studies that led to the eight-year Cabintaxi/Cabinlift development program. The German Government combined the development activities of both firms into the jointly funded program in 1972. The objective of this research and development effort was to devise a transit technology that would be a significant export product with the following characteristics:

1. Small, comfortable vehicles with seats, available at stations and ready for use upon demand

2. Origin-destination operation with no transfers or intermediate stops by use of off-line track at each station.

3. Mainline speed of at least 30 km/hr (18 mph).

4. Complete separation of travel from all other modes by use of elevated guideways throughout the installation.

5. Fully automated operation of the total system.

6. Linear induction propulsion to better control vehicle separation when operating at headways under 10 seconds. Low noise levels and no air pollution were also important objectives.

System definition and laboratory experimentation on components began in 1969. The basis of the control system was developed and tested on a 13 meter, rotary, test fixture during a 16 month period that began in 1972. The first stage of the test facility was completed near Hagen in August, 1973. These facilities consisted of 150 meters of double track guideway (for both supported and suspended vehicles), a merge point, two passenger stations (one at each level) and three vehicles. By October, 1974 the track had been extended to a closed loop with two by-passes and was 1136 meters long. Five vehicles, three above and two below were used for extensive testing. In 1975, the test facility had three stations and nine fully automated vehicles. In October of 1975 a 12-passenger vehicle was introduced for testing. In 1976, the test facility had 1.9 km of guideway, six stations (including those for maintenance and rescue vehicles)and 24 operating vehicles. The emergency evacuation issue was also studied extensively. Testing continued through 1979.

Some of the technical characteristics of the technology were as follows:

Guideway - box girder provides guidance and support for both suspended and supported vehicles

Stations - off-line stations spaced 0.3 to 0.8 km apart; capacity , design dependent, 1,200 vehicles/hr.

Vehicles - For PRT applications - 3 and 12 passenger vehicles demonstrated: 3, 6, 12 and 18 passenger vehicles as well as freight vehicles designed. For non-PRT applications - 12 and 24 passenger vehicles demonstrated for standing passenger applications. One 12-passenger vehicle in operation in a hospital shuttle application.

Propulsion - 2 double-comb linear electric motors, reaction rail mounted horizontally on the box beam girder

Speed - 36 km/hr (22 mph)

Separation between vehicles - 2.5 seconds planned for applications (0.5 seconds demonstrated under test but operational requirements called for a "brick wall" stopping ability, which required the 2.5 seconds separation). For more details on this important capacity-related issue, see this webpage.

Operations - For guideway 20% full: 240 veh/hr or 720 seats/hr for 3-passenger vehicles, 2,880 seats/hr for 12-passenger vehicles. For a guideway 80% full: 2,880 vehicles/hr or 8,640 seats/hr for 3-passenger vehicles; 34,560 seats/hr for 12-passenger vehicles. An example of the 12 passenger vehicle that is in operation is available at the Cabinlift page.

Braking - three independent but blended braking systems were utilized, emergency braking distance of 7 meters was demonstrated. "Brickwall" stopping requirements, under icy conditions, were demonstrated with 2.5 seconds of separation. More details available.

Emergency Evacuation - extensive studies and demonstrations were done to prove that a walkway for emergency evacuation was not needed.

Cabintaxi was a significant research and development effort and was supported 85% by the German Ministry of Research and Technology. Funding for the program reached $70,000,000 by the time the project came to an end. People from around the world visited the test facility. A 20-minute film was produced (with an English sound track) that showed the test track facility in operation and also explains how Cabintaxi could be used in an urban application. This film has also been transferred to videotape and CD-ROM. A photo of a two level stations at the test track is shown below. Photos of vehicles operating on the test track are also provided as are guideway photos. A scale model with a transparent guideway, four illustrations of Cabintaxi stations, several more test track photos and seven architectural renderings are also provided. Two excellent videos are available on-line, one shows Cabintaxi in operation and the other shows Cabinlift in action. The Cabintaxi video is also available on YouTube - see the link at the top of this page. Cabinlift is no longer in operation due
to some changes in the hospital complex that it served.

An extensive application study was conducted for Hagen, Germany,  in 1971-72. A 10-page summary of this study (in English) is available on-line. It includes a map of the proposed areawide network for Hagen and a loading diagram that was derived from simulation studies. It was the first extensive PRT application study ever done.

In 1977, expectations were that an initial installation would be made in Hamburg. The Hamburg transit authority (Hamburg Hochbahn AG) sought approval for a system using 12-passenger vehicles and a final (political) decision to do so was made in October, 1978. The site chosen was in the northern part of the city where a modern business center with office buildings featuring very modern architecture were located. It was estimated that the integration of the Cabintaxi technology in this location would present no problems. The system was to consist of loop 1.2 miles in length, connecting two stations in the office area to the Rubenkamp rapid-rail station. Longer range plans featured 20 miles of double-track guideway and 180 vehicles. Unfortunately, this plan was stopped because of budgetary constraints. Some results from simulation studies conducted in Hamburg are available.  More details on the extensive simulation studies done for Hamburg are also available in a 29 page Summary Report document published in 1979.

The Hamburg project was brought to an end by budget cuts within the German Ministry of Research and Technology. With the end of the only possible project in Europe, the developing firms saw no market for this technology and abandoned activities in this field.  Four years after the German firms withdrew from the field, the United States firm of Cabintaxi Corporation, obtained the rights to this system and is active in the private sector where it looks to be the owner/operator of updated systems based on this technology.

More information about the Cabintaxi technology can be obtained by contacting Marsden Burger, President, Cabintaxi Corporation, 1703 Parker, Detroit, MI 48214; Ph: 313-921-3955, e-mail:

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Last modified: September 20, 2012