Directional and line operations
Directional operation and line operation are the two fundamentally different ways of running rail traffic on a multi-track route and allowing trains to stop at a multi-track station or stop. In directional operation, each track is assigned to a direction and only trains in this direction travel on; In line operation, the tracks are assigned to lines.
Railway lines
In the early days of the railroad, each line was operated independently, often by different railway companies, even if two lines ran in parallel. In the train station, too, the platforms were assigned to the individual routes, and trains only stopped at the platforms that belonged to their route. This is the early form of line operation.
With the increase in rail traffic, the line capacity had to be increased. A major bottleneck on single-track routes is train encounters , so that there is a significantly improved flow of traffic on a double-track route. It is therefore advisable to connect two single-track lines running next to each other with switches and to operate them as a double-track line in one-way operation with several lines.
In the early days of rail traffic, it was still common for the parallel tracks of a company to be counted as part of a line, so there could also be five or six-track lines, which was not uncommon in the Ruhr area. In Germany, however, with the introduction of the register of permissible speeds, it was specified that a line may always have a maximum of two tracks, so that routes with more than two tracks were assigned to different lines. Usually two parallel tracks were assigned to a certain route (colloquially also line ), the formerly multi-track route thus divided into several double-track routes in line operation. In rare cases, multi-track lines were also divided into "inner" and "outer" lines, such as B. on the Hohenzollern Bridge between Cologne main station and Cologne Messe / Deutz station .
Advantages and disadvantages
If several parallel, double-track lines are used in directional operation, the additional tracks serve as overtaking tracks, or there is a separation of slow and fast traffic from the outset. The advantages of directional operation arise z. B. in a four-track route (here with right-hand traffic as a regular schedule), in which the two inner tracks are intended for faster trains, z. B. on the Remsbahn between Stuttgart-Bad Cannstatt station and Waiblingen station :
- The route allocation is planned in such a way that in the event of a possible overtaking, the slower train changes to the "slower track". A medium-speed regional express can therefore run on the “faster” or the “slower track”, depending on whether there is a conflict with a regional train or a long-distance express train. In order for this to be possible, there must be a sufficient number of transition points with associated signaling on the route.
- With regular service, however, long-distance trains would have to use the “faster pair of tracks” and local trains the slower one. Other train types (such as Regio-Express) and freight trains would then also have to be assigned to one of the two routes, since a change of route is only possible after crossing a track in the opposite direction. This is possible with the appropriate structural conditions (switches, signals, etc.), but may lead to delays in operations due to the necessary blocking of the opposite track.
The disadvantage of directional operation are the expensive overpasses that are required to be able to link different routes level-free , e.g. B. when entering a train station. Furthermore, train stations in directional operation need their own turning tracks or systems for turning trains. Turning trains cross and temporarily block other tracks in order to get to their turning track.
Further examples
- Today, double-track routes are almost always used in one direction. A major exception are two parallel single-track lines that run together in front of a hub station in the integral timetable , e.g. B. Hervest-Dorsten train station . Since trains in the direction of the junction station arrive at about the same time and later depart at the same time, it is advantageous to assign the two tracks to the lines, not the directions.
- An interesting situation arises in the case of routes with three tracks, as they are e.g. B. often occur in connection with S-Bahn. If a double-track line no longer offers enough capacity, a third track may be added. If the S-Bahn uses a different electricity system from the rest of the railway (such as the S-Bahn in Berlin and Hamburg), the S-Bahn and other trains cannot run on the same track and there is only one line operation . In the other case, one has to weigh up between directional and regular traffic. In one-way traffic on a three-track line, the middle track is in track changing mode , e.g. B. Bremen – Buchholz or Kinzig Valley Railway .
- In a route with more than two tracks in regular service, two parallel tracks usually belong to an independent route. A three-track line can therefore consist of a single-track line alongside a double-track line in one-way operation. This distinction is made especially when trains can under no circumstances switch from one route to the next adjacent route. This can be due to missing switches or different power systems.
- Since Duisburg Central Station is purely a directional station (see below), while Düsseldorf Central Station is a pure line station, the Duisburg – Düsseldorf line is changing from a five-track route in purely directional operation to a six-track route in mixed direction and line operation - the two tracks of the Long-distance railway lines will be merged on the eastern part of the route, while the two S-Bahn tracks will continue to be flanked by two local tracks. Between the Duisburg-Großenbaum train station and the Düsseldorf Airport train station , the route is reduced to a four-track line in regular service; shortly before the Düsseldorf-Unterrath train station , the route becomes six-track in pure regular service again, thanks to the leveling of the local tracks.
Train stations
First of all, every track in a train station can belong to a line operation or a line operation. As a rule, a train station has more platform tracks than mainline tracks; these are simply evidenced by fanning out the tracks. In the example of four platform edges on a three-track line, the track of the single-track line could thread onto two platform edges and the other two tracks onto another two platform edges. The station is then also in regular service. In practice, this could be a station where the single-track line ends or has a train crossing point, while on the double-track line, trains simply stop.
In the case of the same route in directional operation, the station would have two platform edges in each direction. He could e.g. B. serve as an overtaking or transfer station on the three-track line. Trains could also turn around on the inner platforms without coming into conflict with an outside train.
Since there are usually two platform tracks on a platform, the above arrangement can be changed without changing the track plan (and thus without additional travel conflicts) by creating the platforms. In the example of the line operation, the single-track line could also occupy the house platform and one side of a central platform, while the double-track line would have the other side and an outside platform. This creates a connection on the same platform at least in one direction. Something similar can happen in the case of one-way traffic: long-distance trains run on the house platform and the outer platform, and regional trains run on the two tracks of the central platform. In this case, the station is in regular service (middle versus outer platforms), although the line is still in directional operation (direction A, passing track, direction B).
In the case of larger train stations, however, flyover structures are often necessary to establish the desired operation at the train station . The S-Bahn in the Ruhr area, Hanover, Nuremberg and Mannheim / Heidelberg have z. B. own platforms in the respective stations, which can be reached by crossing the tracks created for the S-Bahn. The S-Bahn trains sometimes run in the same direction as other trains on the outer branches, and the overpass leads them into the S-Bahn section of the station. There, the S-Bahn often has several platforms that are in directional operation to one another, but in line operation with respect to the remaining platforms.
Frankfurt Hauptwache and Konstablerwache are an example of two stopping points on a route with different modes of operation and without Geis overpasses in between . On the route, the two tracks of the S-Bahn run in the middle between the two tracks of the U-Bahn. In Hauptwache station, the S-Bahn has a central platform and the U-Bahn has two outer platforms, in Konstablerwache station there is a combined platform for each direction, where you can change between the U-Bahn and S-Bahn in each direction.
Directional platforms on subways
Because of the high density of trains, underground and light rail vehicles almost always run on double-track routes. Directional operation takes place when two lines share a double-track line. See Linking Station .
In the simplest case, a subway transfer station consists of two nearby stops on two different routes that are connected by a (as short as possible) footpath. A special case of this is the tower station , where the two stops are directly above each other and thus create a particularly short footpath connection. In any case, this use corresponds to line operation.
If two high-speed rail lines run in parallel on one section, each line retains its pair of tracks, because a transition would slow down operations due to the necessary signaling. For a train station located on this section, the platforms can in turn be divided between the lines by having one track of each route on both sides of a platform. This can be done like in an above-ground train station with adjacent tracks and platforms. The usual method for underground stations is now to lay two platforms parallel on top of each other. Each platform is then served in one direction and each side of the platform is assigned to a line. This construction takes up only a little more space in width than a normal subway station. The greater width results from the wider platforms required by the transfer function, which also have to accommodate more or wider stairs than usual.
In both cases, a direction station can also be used to branch lines. For this purpose, a track change or a flyover structure only needs to be created at the exit of the directional platforms. As a rule, you build a double track change because you gain operational flexibility with low costs. With the system as a direction station, such a station is automatically free of elevation , but only in one direction. This is explained using the example of Munich Innsbrucker Ring . The U5 runs from the city center in the direction of Neuperlach and the U2 runs from another city center route in the direction of the exhibition center. During rush hour , the U7 amplifier line also runs from the U2 inner-city route towards Neuperlach. Trains in this direction can enter and exit without interfering with the existing lines. However, it is not possible to use a line from the U5 inner-city route to the exhibition center at the same time. For this purpose, the track bridges would have to be rebuilt. An example of such a renovation is the Berliner Tor underground station in Hamburg, where the eastern line routes of the U2 and U3 were swapped with the help of a renovation that lasted from 2006 to 2009.
In contrast to the tower station, a direction station does not also contain a route crossing. Each route uses one side of the station. Often the routes do not even cross near the train station, they just touch. This applies e.g. B. for the (only partially in operation) direction stations Jungfernheide and Rathaus Steglitz of the Berlin U-Bahn . If a route crossing is desired, this can be done in front of or behind the station by crossing the two pairs of tracks.
The New York subway has several four-track routes that are operated in one direction. The "Local" lines run on the outer tracks and stop at outer platforms, while at the fewer stops of the "Express" lines island platforms between the outer and inner tracks allow you to change between more frequent local trains and less frequent express trains.
literature
- Jörn Pachl: System technology for rail transport. Plan, control and secure rail operations . Vieweg + Teubner, 2004, ISBN 3-5193-6383-6