Frankfurt U-Bahn

The Frankfurt U-Bahn is a Stadtbahn (premetro) system serving Frankfurt, Hesse, Germany. Together with the Rhine-Main S-Bahn and the Frankfurt Straßenbahn, it forms the backbone of the public transport system in Frankfurt. Its name derives from the German term for underground, Untergrundbahn. Since 1996, the U-Bahn has been owned and operated by (VGF), the public transport company of Frankfurt, and is part of the Rhein-Main-Verkehrsverbund (RMV) transport association. The licence contract is up to 31 December 2031 and is renewable. The contracting authority of VGF is the municipal transport company.

The U-Bahn opened in 1968, and has been expanded several times. It consists of three inner-city tunnels and above-ground lines in the suburbs. About 59% of the track length is underground. The network operates in a variety of right of ways typical of a light rail system, with above-ground sections operating on street and core sections running underground in the inner city.

Like all public transport lines in Frankfurt, the system has been integrated in the Rhein-Main Verkehrsverbund (RMV) since 1995. From 1974 until the founding of the RMV, the Stadtwerke were shareholders in the predecessor group, the Frankfurter Verkehrsverbund (FVV; Frankfurt Transport Association).

The network consists of 86 stations on nine lines, with a total length of 64.85 km. Eight of the nine lines travel through the city center (line U9 being the exception). In 2016, the U-Bahn carried 132.2 million passengers, an average of approximately 361,200 passengers per day. Most recently, on 12 December 2010, two new lines were added, the U8 and the U9 (both part of the long-planned but only partially completed fourth route), which opened up the university campus area and the new development area on Riedberg.

History
At the beginning of the 1950s, the first plans were made to relieve the then already overburdened tram. More than 100,000 motor vehicles were registered in Frankfurt in 1958, and more than 180,000 commuters used the transport infrastructure on a daily basis. Various alternatives to the construction of a modern high-speed traffic system and the separation of above-ground traffic flows were discussed. On 5 April 1960, the SPD faction requested that the city council might commit to a two-line straddle-beam monorail system designed by Alweg. Lord Mayor Werner Bockelmann, however, advocated from the outset the construction of a U-Bahn, which was however considered the most expensive option. On 7 July 1960, the city council therefore commissioned a city planner with the preparation of a general planning overview in order to compare the costs of the three systems: Alweg straddle-beam monorail, U-Bahn and Stadtbahn (premetro). Responsible for the planning was in October 1961 designated to the head of the Traffic Department Walter Möller. The decision was finally made in late 1961 in favour of a U-Bahn system, which was to be built in several sections initially using existing tram infrastructure. In the first construction phase, the tunnels of the inner city were to be built for the time being, which were to be connected via provisional ramps to the adjacent tram routes. It was not until the second construction phase that the tunnels were to be extended beyond the inner city and connected to suitable upgraded above-ground routes in the suburbs. In the third construction phase, the change from Stadtbahn to U-Bahn would have been completed, which was to operate completely independently of traffic in tunnels, cuts and dams.

On 28 June 1963 the first pile of rubble for the construction of the 3.2 km-long tunnel under the Eschersheimer Landstraße. For the first stage of development until 1975 - approximately corresponding to today's main lines A and B - construction costs of 565 million DM were expected. The new Lord Mayor Willi Brundert compared the "boldly begun subway construction" in 1964 in its dimensions with the medieval cathedral building.

After just one year, the ambitious mammoth project threatened to fail due to financing problems. Falling tax revenues and a tax policy geared towards federal and state governments drove the municipalities close to ruin in the mid-1960s. Frankfurt was 1.4 billion DM in debt in 1964, the most heavily indebted city in Germany, with a regular budget of 733 million DM. Under pressure to stabilize the budget deficit, the 1964–65 municipal assembly reduced long-term investment planning from 2.7 billion DM to 1.7 billion DM and even hinted that for some time that Eschersheimer Landstraße would be "impassable desert" after completion of the tunnelling work.

The U-Bahn opened on 4 October 1968, with the first route running from Hauptwache to Nordweststadt (now line U1). This first section ended up costing 344 million DM to construct, of which the federal government contributed 56 million DM and the state of Hesse contributed 129 million DM.

Current lines
The U-Bahn consists of nine lines, U1 to U9, running on three primary routes based on the three tunnels, with a planned fourth route from Ginnheim in the suburbs to Frankfurt Hauptbahnhof only partially completed.

The route network consists of the four routes "A", "B", "C" and "D" of the standard gauge of. The operating length of all routes is 64.85 km. Central sections of the route are called "basic route" or "trunk route"; these branch out into several "connecting lines", which are usually driven by only one line and are sometimes referred to as "upgraded lines". The terms "basic section" and "connecting section" and their designations are based on the names of the construction sections. Sections of the legs were designated by the letter of the route and a Roman numerical suffix - sections of the connecting lines with an Arabic numeral. The designation of the connecting lines "A1", "A2", "A3" and "B1" was also used to designate the lines until 1978.

Like all light rail vehicles, trams and subways in Germany, the Frankfurt U-Bahn is subject to the regulations of the tram construction and operating regulations (BOStrab). The tunnels as well as the above-ground section between Römerstadt and Ginnheim are completely developed as independent railway tracks, most of the other aboveground sections partly as an independent building, partly as a special track. These sections have numerous level crossings for road traffic and pedestrians. The U5 operates in the section between Friedberger Anlage and Marbachweg largely on street-level railway body.

Tunnels exist at -
 * A Line: South of Dornbusch, into the city centre, Nordwestzentrum (small section)
 * B Line: Scheffeleck and Seckbacher Landstraße to Bockenheimer Warte.
 * C Line: Kirchplatz to Johanna-Tesch-Platz and Ostbahnhof

Routings
These are individual routings.



Future plans

 * Europaviertal branch for Line U5
 * Closure of the Ginnheim–Bockenheimer Warte gap (currently served only by the ground-level tram system)

Depots

 * Heddernheim - for A & D Lines
 * Ost - for B & C Lines

U1 Class
The U1 Class consists of two six-axle, two-section prototype vehicles made by Duewag in 1965, derived from the previous tramcars. Delivered in unpainted livery and later painted all red, it was used from 1966 to 1976 and was one of the world's first modern LRVs. The vehicles were removed from service after ten years because it was incompatible with newer types. A copy of a U1 Class is now stored in the Frankfurt Transport Museum.

U2 Class
The U2 Class were the first production vehicles for the network. Duewag built 97 vehicles of this type in three batches from 1968 to 1978. A fire at the depot in 1980 destroyed five sets and were replaced with seven replica sets in 1984. They were painted in a red and white livery and used from 1968 to 2016. A variant, the U2h, features a lower boarding height than the regular U2, and was in use until 2013.

The U2e was a planned refurbishment set for 2015, but due to age constraints, U2 cars were replaced with the newest U5 class over U2e. The last U2 car was withdrawn after a farewell trip on 3 April 2016, after over 48 years of service. U2h examples such as 303, 304 and 305 have been preserved.

Siemens adapted the U2 design for the North American light rail market, making the U2 the first modern LRV car in North America, currently in use in Edmonton and Calgary. San Diego used these sets until 2015.

U3 Class
The U3 Class is based on the U2, but have a slightly longer length, a lightweight design made entirely of steel, and was intended for underground operation. Duewag built 27 vehicles, which are painted in the present blue livery that was applied to RMV (formerly FVV) and have been in use since 1980. They were deployed on line U4, until being replaced in April 2015 by U5 train cars and transferred to line U6. In June 2017 the last type U5 car was delivered, which matched the retirement of type U3 train from service. After October 2019, most trains were refurbished and transferred to Monterrey Metro in Mexico.

U4 class
The U4 class is developed from the U3 class, technically based on and similar in appearance to the R type trams. Siemens/Duewag built 39 vehicles numbered 501–539 between 1994 and 1998, which have also received the current blue livery. They were originally deployed on lines U1, U2 and U3, and later on lines U8 and U9. An accident involving the two cars 517 and 532 on 28 February 2007 resulted in their early retirement from the fleet and being scrapped for spare parts. Since July 2010, all remaining U4 cars are going to be refurbished and get new yellow handrails to help color-blind people to orienting, as well as an air conditioning system in the cockpit until July 2017. Starting in March 2016, all cars should receive new white LED displays as a replacement for the aging flip-dot displays. The process was scheduled to complete in mid-2020.

U5 Class
The U5 Class, the newest of the U-Bahn fleet, has been produced by Bombardier Transportation and Alstom in Bautzen since 2008. The first order of 146 vehicles was placed in 2005 and another order of 78 cars came in 2011. Two cars were damaged in a fire at the production factory in 2010. They have been deployed to all lines and will gradually replace the older cars in the coming years.

There are three subtypes of the U5 class: the U5-25, which consists of two-section articulated sets like the older cars, while the U5-50 is formed of two sets derived from the U5-25, where one cab each has been replaced by a gangway which connects the two sets. The concept is similar to the TW 2000 used on the Hanover Stadtbahn. The third type has been internally designated "U5-KR", short for "U5 Keine Richtung" (no direction, a naming convention originating from the naming scheme for bidirectional vs one-directional tram sets: "ZR - ZweiRichtung", "ER - EinRichtung), which stems from its bilateral lack of a permanent cab. Both sides of the EMU are outfitted with merely a gangway, so that they can be coupled between two U5-50 sets, which forms a continually walk-through consist of either 75 metres (U5-50<->U5-KR<->U5-50), or up to 100 metres (U5-50<->U5-KR<->U5-KR<->U5-50). The maximum length consist has been dubbed "U5-100" by VGF. Each cabless end is also equipped with a dashboard in order to facilitate shunting, as well as sliding doors (for closing up the train during movements with the cabless end free from a consist), and head/tail lights.

Tram/Hybrid LRV
The P/Pt/Ptb Class was used from 1978 to 2016 on the U-Bahn network. While the first batch of vehicles had been ordered outfitted with folding steps, to facilitate the transition from a tram to a light rail (high floor) service, the second batch had not and thus was initially incompatible with operating on the "U-Bahn" lines. To differentiate the two subclasses, the batch with folding steps was designated "Pt" (for "tunnelgängig", operable in tunnels). Upon opening of section C of the network, the batch that had been delivered without folding steps was thus upgraded, in order to be operated on line U7. To make this possible, the platforms had been modified, in order to accommodate the narrower body of the Pt. Once enough other stock had been made expendable on other lines, the need for interoperability arose, and so an overhaul was necessary, during which the steps were modified in order to make up for the difference in width between the Pt and other light rail types. The resulting subclass was then named "Ptb", the b standing for "breit" (wide). The aforementioned modifications to the platforms were reversed as well. While all other lines did not require the feature of the folding steps anymore, the Ptb remained indispensable on line U5 where on certain sections the stations had not yet been outfitted with high floor platforms, much in the style of the transitional period for which the Pt had been ordered. As the line was gradually upgraded with high-level platforms as used on the remainder of the network, the Ptb class cars had their widened steps restored to regular width and were repurposed for a time on tram lines 15, 17, and 20, filling in due to a tram stock shortage.