Symmetry minute
The symmetry minute is a characteristic measure in interval timetables of public transport. At this time, encountered a ride in a regular timetable to its counterpart on the same line. Transfer times between lines with identical symmetry minutes are always the same in both directions.
- 5.1 The "jumping " symmetry minute
- 5.2 Large deviations
- 5.3 Minor deviations: S-Bahn Munich
Introduction
In a regular timetable, the trains (or other transport ) run at regular intervals, which usually amount to fractions or multiples of one hour. This makes them go in different hours on the same minutes. The same is true for the opposite direction. Thus, the traits of a line in both directions meet always the same minutes an hour.
At this time symmetry is the roadmap of the direction and the opposite direction "mirrored". At the line end points the center of the turning point coincides with the symmetry minute. The distance between two successive periods of symmetry is equal to half the cycle time. In an hour it comes every 30 minutes to an intersection with the trains of the same line. With a pitch of two hours, the time symmetry repeated hourly.
In principle, a crossing will be determined at any time. Usually, however, a uniform time symmetry is used for the travel times on several or all lines in a network for convenience. For most railways in Central Europe and a few other transportation companies symmetry time is set so that the trains always meet approximately 58 ½ minutes of symmetry. In one hour there is another symmetry time at minute 28 ½, with even denser clocks accordingly more often.
The following table is used for easy reading of the time of departure the opposite direction at hourly intervals. Here, in Central Europe far the most commonly encountered symmetry minute basis. For shorter pulses the other departure times can be calculated on this basis. In the last line of the bars are given to the respective meeting times.
As one 15-minute cycles are rarely encountered, the yellow shaded encounters appear not often, but for instance on the local railway Vienna -Baden, on the Trogenerbahn and on the interurban tram Liberec Jablonec nad Nisou.
Basics
In an n - minutes new symmetry node yield per hour, these are the points in time at which meet two trips the same line. For hourly tours example, there are two symmetry minutes per hour, see table above. Generally there is a symmetry minute on a line from
With the arrival in the back and the departure time of the trip at any stop ( or the corresponding transit times at any location ). In an hour, there is another symmetry minute to 30 minutes added to this in an even denser clock there is further symmetry minutes, which are each apart.
A symmetry node does not necessarily lie in a train station, where travelers get on or off, but can also lie between those stations. On single-track lines, however, an alternative possibility must be present here, what the leeway concentrated.
A passenger can be determined by knowing the symmetry minute with known arrival minute at a regular interval timetable immediately exit minutes in the opposite direction approximately.
The symmetry minute is also important for Connecting: When traveling from a location A to a specific route for a place B on a different route back and the transfer time is also in the opposite direction, only the same if the two routes have the same symmetry time. At different times of symmetry is that the difference between the transfer times of the direction and the opposite direction is always equal to twice the difference of the times of symmetry.
The waiting time of the transport network at the crossing points may be different. At a crossroads of different train types, for example, waiting for a local train until the faster train, which does not exist at the time in the opposite direction because of another clock has passed. Likewise, the speed in different directions may be different ( see example). Both results in deviations from the symmetrical course.
2 -hour intervals
In Mannheim, for example, be the two hourly free ICE lines 11 and 12 replaced in the clock node on the half hour with the lines 42 and 43 per hour, and in such a way that trains the same line always meet in their respective path just before the hour. In Mannheim, therefore always encounter different trains ICE lines.
For a 2 -hour intervals to departure times result in different numbers of hours each direction. If you arrive in a direction even hour (eg 14:40 ), exit the opposite direction is always odd hour (eg 15:17 ) and vice versa (in the examples was again assumed that the symmetry minute 58 ½). A clock skew one direction by one hour results for both directions of departure hours at the same even or odd hours. Exception to remain ( approximately ) full hour in this case runs.
In some regions, such as Brandenburg, these clock offset is applied at 2 -hour intervals often. Examples are the EVB on the railway line Bremerhaven Buxtehude and the Rügenscher Bäderbahn ( with the usual strongly deviating symmetry minute). If this does not happen across the network, this leads to different ports in the direction and the opposite direction. So you have Sundays in Bremerhaven a direct connection of Bremervörde to Cuxhaven, but must wait in the opposite direction over an hour.
The formation of circulation networks can provide operational benefits arise depending on the travel time on the routes and beat long waiting times of the vehicles at the ends. Ends there several lines that go in a clock to " alternate ", the incoming vehicles can one directly continue on the other; you save vehicles without deteriorating the offer.
Practice examples
Netherlands, Belgium, Czech Republic
The Nederlandse Spoorwegen had a regular timetable for a long time before 10 December 2006 - the beginnings date back to 1934. Under the name " Spoorslag '70 " a clock schedule with a contemporary practice of the other European railways outlying symmetry time at minute 16 and 46 was 1970/71 introduced.
With the annual timetable 2007, the Nederlandse Spoorwegen introduced a symmetry of time, a minute 00 /30. This regulation also exists in the Belgian Knooppuntdienstregeling ( node table).
The Czech Railways used on routes with a clock schedule, such as Prague Cheb, usually agreed in the German-speaking symmetry minute. In contrast, the symmetry of time is in some other European countries exactly on the hour.
Example Mettmann
Consider the accompanying picture timetable for the railway line between KBS 450.28 Mettmann City Forest and Dusseldorf -Bilk, on the upside the S28 from Mettmann to Kaarst. From Dusseldorf Gerresheim also runs the S8 from Wuppertal to Mönchengladbach on this route under KBS 450.8. The plan can be found in the following:
- Both lines run in a 20 -stroke.
- The S8 meets itself at 10, 30 and 50 in Dusseldorf main station; more, not illustrated, matches must take place at 0, 20 and 40 to get to six symmetry nodes. These meetings can also be guessed by the chart. An obvious symmetry minute is therefore 0
- The S28 meets itself at 10, 30 and 50 in Bilk. The encounters between Gerresheim and Flingern find not as expected by 0, 20 and 40, but ½ ' instead of later. Reason is the following: A timely meeting would take place according to the plan in Gerresheim. There the route for the S28 is only single track passable. This also has an impact on the encounter between Neanderthal and Erkrath that does not take place also on time.
- In Bilk, where both lines have the same symmetry minute 0, the transfer times for both directions are equal: 6 ' Mettmann -Mönchengladbach and 14' for Wuppertal- Kaarst. In Gerresheim where the symmetry minutes no longer match, the transfer times for different directions are not equal, for example, 18 ' from Mettmann to Wuppertal, but only 1 ' from Wuppertal to Mettmann.
Connections on the instance of Bielefeld
Consider the single-track branch lines Paderborn Bielefeld and Osnabrück, Bielefeld. At the Bielefeld - Brackwede station can be reached due to the too short distance to the crossing point at Senne city connections are not. It caused delays of about an hour. From the adjacent picture schedule can be read off exactly this:
- The two lines have different symmetry minutes. For driving on Senne city line symmetry minute is 57 ½, for the circulating about Steinhagen line at 53 It follows that the transfer times in the different directions are not equal; in the graphic timetable can the see well.
- Both pairs of trains intersect in the diagram just above Brackwede. There transiting passengers from NWB 75 564 Senne city (first line pair) and NCA 75424 to Steinhagen (second line pair) must wait almost an hour for the next train because NWB NWB 75425 or 75577 are just left. From Bielefeld the connection would be good though; unfortunately start there both trains, so in Brackwede no passengers will board from Bielefeld.
Long waiting times at a change junctions can have line losses to subsequent node stations result. To improve connection times the points of symmetry of individual lines can be moved, but mostly it does not go with single lines. Another possibility is the consideration of passenger flows at peak times. Due to clock skews in the morning or afternoon traffic connection times of stronger direction used to the detriment of the weaker traffic stream can be improved, but that requires a departure from symmetry solid minutes.
Differing systems
The "jumping " symmetry minute
Often found on single-track lines with older signaling the trains a few minutes after the event on a crossing station. It may also happen that a stretch in one direction is traveled faster than in the other. This has the consequence that only a part of the track has the usual symmetry time, the other portion, however, a shifted to several minutes.
Larger deviations
Insist on individual railroads larger deviations, for example at the Mariazell Railway, the Heidekrautbahn in Berlin, the Oberwesterwald train from Limburg to Au (Sieg), Rhön web between Fulda and Gersfeld or Bayerische Oberland Bahn.
The line S1 S-Bahn Salzburg has a symmetry of 52 ½ minutes. Consequence of this is that the transfer times at the Salzburg train station to other lines in one direction are longer by about 13 minutes than in the opposite direction. The arrival of the line the minute 45 ( or 15) and thus corresponds to the usual times of arrival at railway stations, the departure time is equal to the target with a symmetry minute 58 ½ time on the hour (this can arise and tight connections to some IC / OEEC / transport lines). Overall, this major difference to the usual symmetry of time has little impact - for example, the S3 is missed in one direction.
Throughout the Hamburg high-speed rail network ( S- Bahn, U -Bahn and partially AKN railway) is the symmetry minute with a few exceptions for a few seconds after minute 31
Minor deviations: S-Bahn Munich
On the main line of the Munich S -Bahn, the symmetry time is two minutes later than usual, so half a minute after: 00 The following simplified representation is a "snapshot" of such specification, also valid for the 20.5 and 40.5 minutes due to the 20 -minute clock.
S3 - (S2 ) - S4 - S1 - S8 - (S3 ) - S2 - S6 - S7 - (S8 ) (in brackets amplifier units )
From left to right, from West to East: Trains the S3 meet just about at the Donnersbergerbrücke to the hacker bridge is at the same time ( during rush hour ) crossing the compressor trains of S2, between main station and Karlsplatz meet the guidelines of the S4. At the same meet as the Marienplatz, the trains of S1, Isar Gate on the S8.
Offset by ten minutes, this applies to the other five routes.
Inner-city transport
Also, intra- urban transport networks often have a uniform symmetry time. This is especially true for night networks and modern city bus systems in smaller cities.
Also, all subway lines in Munich ( with some exceptions in the rush hour, and generally U4 and U6, aside ) and most tram lines have a uniform symmetry minute. The timetable change on 15 December 2013, this was changed to zero symmetry. From this result matches to Minute 0:00 (20 -minute intervals ), or additionally 5:00 ( 10 minutes), which can be observed on the running simultaneously at certain stops in both directions: for example Heimeranplatz and Max Weber space on the U5, Columbus Square and the main railway station on the U1 ( except during the morning rush ), Fraunhofer road on the U2, Implerstraße on the U3, Scheidplatz simultaneously on U2 and U3. Similar to the hourly results for the 10 -minute clock in Munich adjacent table. The sum in each row 0 and 10; can apparently resulting sum - 9 by rounding the figurehead ends timetables themselves - only.
Other cities, such as Braunschweig, Chemnitz, Halle ( Saale), Hannover, Linz ( Danube ), however, are based in this respect on the rail and have the symmetry of time consequently at 3:30 or 8:30, although deviations here because of the dense clock not so very consequence.
In inner-city tram and bus networks, there are reasons of optimization is becoming more common circulation networks, with more than two lines, such as in Kassel and Nuremberg. This is favored since the earlier required time-consuming changes of train destination signs deleted by the technique of the matrix display of line and destination.