SelTrac
SelTrac (also SELTrac or SELTRAC) is an operational sequence control for rail-bound local traffic that enables the fully automatic operation of trains . The system was developed by Standard Elektrik Lorenz (SEL) and tested and used in West Berlin on small-profile lines of the subway . The system can reduce the distance between two trains on the braking distance and thereby significantly increase the train frequency. The name stands for S tandard E Lektrik L orenz Trac .
Trial operation at the Gleisdreieck
In the course of the closure of the sector border between West and East Berlin on August 13, 1961, operations on the section between the Gleisdreieck and Potsdamer Platz underground stations of today's underground line 2 were suspended. From January 1, 1972, there was no longer any U-Bhn train running on the elevated railway between Gleisdreieck and Wittenbergplatz .
With funds from the Federal Ministry for Research and Technology, the SEL company began a field test in the first half of 1977 on the 833 m long disused section between the elevated railway stations at Bülowstrasse and Gleisdreieck (below). The test route ended in front of the Bülowstraße train station, which was then rented as commercial space. In the second half of the year, it was extended to the sector boundary until shortly before the parking area of the Potsdamer Platz underground station. This meant that a roughly 1650 m long, predominantly two-track line was available for trial operation. The double railcars 856/857 and 848/849 of the A3L series were converted accordingly. Since there was an operating track at the Gleisdreieck to the underground line 1 , the vehicles could be fed by rail. The first test drives took place in May 1977.
The experimental operation in 1977 concentrated mainly on the operational demonstration of the various functions of the operational sequence control: automatic travel, point travel, interlocking control, malfunctions in the multi-computer system, train formation, safety reactions and special operational cases such as protection travel, coupling travel and temporary slow speed points. In that year, the two test vehicles covered around 12,000 km. In 1978 the company was used for endurance testing of the various automation components. The two vehicles together covered more than 42,000 km, which corresponds to a daily mileage of approx. 120 km per vehicle.
In the spring of 1978, switching between on-board control units was successfully tested in a train. Reliability testing continued on this test track until autumn 1981.
Operation on the U4 in Berlin
As a second stage of the system testing, reference operation on underground line 4 began on May 4, 1981 . This was chosen because it runs independently of the other lines and can be operated as a closed system. The purpose of the reference route was to test the SELTRAC system under everyday conditions, to gain further experience and to demonstrate the system to potential customers. The track was completely revised in terms of the superstructure; The line conductor was laid in the track, the signal systems were expanded and television cameras were installed in the subway stations to monitor the change of passengers. A control center for line 4 has been set up in the regional signal box at Nollendorfplatz.
Between 1978 and 1980, 16 double railcars of the then most modern small-profile class A3L were equipped for automatic train operation in the main workshop in Grunewald. In addition to the necessary transmitting and receiving systems, the vehicles received a computer system to control the train and the dialog with the control center as well as a loudspeaker system. Four double railcars were also equipped with additional means of passenger information (leaflet displays on the fronts, small pallet displays and intercom in the passenger compartment). The free use of all these cars in the small profile network was retained. The 16 vehicles were the following double multiple units: 682/683, 684/685, 688/689, 690/691, 692/693, 696/697, 700/701, 702/703, 706/707, 708 / 709, 712/713, 716/717, 718/719, 732/733, 748/749 and 758/559.
The trial operation on Line 4 between 1981 and 1985 served to prepare for acceptance by the technical supervisory authority, which was essential for use in regular operation. The automatically controlled trains drove without passengers between the normal regular trains, during the nightly breaks in operation could be driven fully automatically. The light signals were still valid until September 1985 and the magnetic travel locks remained active. In order to be able to intervene in the event of danger, the drivers remained on the trains, and the train dispatchers on the platforms were also at their posts for observation.
For the approval of the system in public transport, an intensive functional and safety operation under observation of all components was set for the period from September 10 to 27, 1985, daily from 8 a.m. to 1 p.m. 14 two-car trains (one double multiple unit each) were used on the almost 3 km long route, so that a dense train traffic built up every 90 to 50 seconds. They were all staffed, but the drivers had purely observational tasks.
After the end of continuous operation, approval of the SELTRAC system in passenger traffic was granted. However, the central processing was kept as a change in the door monitoring would have been necessary for fully automatic operation. One of the points of criticism was the lack of recognition of obstacles in the track bed. In other worldwide applications, platform screen doors later replaced this defect, contact mats identified people or objects above a certain weight, or the local supervisory authorities did not require any special inspection of the tracks.
At the end of 1985, SEL withdrew from the Berlin facility. The system technology was handed over to the Berliner Verkehrsbetriebe (BVG) for further use , which continued to operate the system. SEL remained available to troubleshoot problems. In the mid-1990s, there was an increasing number of malfunctions on the on-board computers that would have had to be replaced due to age. As the SELTRAC trains were no longer compatible with conventional trains after modifications from 1988 onwards, their use was limited from then on. At the end of 1993, fully automatic operation on the line, now known as the U4, ended, and in 1995 the BVG board decided to finally end the SELTRAC system.
From 1988 a BVG-owned attempt followed with regard to the future self-handling of train drivers (ZSA). The SELTRAC trains were ideal for testing them, as they already had electrical door mechanics, monitoring of door emergency opening, signaling technology for door opening, technical start-up lock when the doors were open, side-dependent door opening and loudspeakers. In the spring of 1992 the ZSA tests began on the U4, from which the later driver self-handling, as it is used today in the Berlin subway, developed.
The double multiple units 684/685 and 732/733 were converted into auxiliary equipment trains for the small-profile network in the years 2000/2001, all others were retired by June 2010.
Further development
The SELTRAC system was further developed and is now used by numerous railways. Examples are:
- Jubilee, Northern and Piccadilly Lines from London Underground
- Docklands Light Railway
- SkyTrain Vancouver
- AirTrain JFK
- Beijing Subway Line 4
- Dubai Metro