Track layout guide - Revision history

Qhfreddy at 12:01, 1 May 2023

2023-05-01T12:01:54Z

← Older revision		Revision as of 12:01, 1 May 2023
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	An example of this problem can be seen at [https://www.openstreetmap.org/#map=16/51.6080/-1.2238 Didcot on the GWML], where [https://youtu.be/v67ycpmAEHc?t=2148 a fast train going from Reading to Oxford has to cross the opposite fast line, and both slow lines to take the branch towards Oxford]. The single train is effectively occupying all 4 tracks for a span of 6 minutes if we assume a typical 3 minute headway before and after the train.		An example of this problem can be seen at [https://www.openstreetmap.org/#map=16/51.6080/-1.2238 Didcot on the GWML], where [https://youtu.be/v67ycpmAEHc?t=2148 a fast train going from Reading to Oxford has to cross the opposite fast line, and both slow lines to take the branch towards Oxford]. The single train is effectively occupying all 4 tracks for a span of 6 minutes if we assume a typical 3 minute headway before and after the train.



	FU-FD-SU-SD		FU-FD-SU-SD
Line 188:		Line 190:
	Impractical to allow trains to		Impractical to allow trains to

	Direction paired		=== Direction paired ===

	FU-SU-SD-FD or SU-FU-FD-SD		FU-SU-SD-FD or SU-FU-FD-SD

Qhfreddy: /* Fast-slow separation */

2023-03-16T10:19:39Z

Fast-slow separation

← Older revision		Revision as of 10:19, 16 March 2023
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	This advantage however only really exists for at grade junctions, for grade separated junctions, speed paired quad track will usually take up more space than direction paired (see for example. Also, if branching tracks join from either side of the main lines, extra bridges will be needed to avoid crossing the fast tracks. Furthermore, it is basically not possible for trains to easily go from the slow tracks to the fast tracks without creating a nightmare of path crossings or a complicated set of flyovers. For these reasons, the use of speed paired quad tracks should generally be avoided.		This advantage however only really exists for at grade junctions, for grade separated junctions, speed paired quad track will usually take up more space than direction paired (see for example. Also, if branching tracks join from either side of the main lines, extra bridges will be needed to avoid crossing the fast tracks. Furthermore, it is basically not possible for trains to easily go from the slow tracks to the fast tracks without creating a nightmare of path crossings or a complicated set of flyovers. For these reasons, the use of speed paired quad tracks should generally be avoided.

			An example of this problem can be seen at [https://www.openstreetmap.org/#map=16/51.6080/-1.2238 Didcot on the GWML], where [https://youtu.be/v67ycpmAEHc?t=2148 a fast train going from Reading to Oxford has to cross the opposite fast line, and both slow lines to take the branch towards Oxford]. The single train is effectively occupying all 4 tracks for a span of 6 minutes if we assume a typical 3 minute headway before and after the train.

	FU-FD-SU-SD		FU-FD-SU-SD

Qhfreddy: /* Speed paired quad track */

2023-03-16T08:49:54Z

Speed paired quad track

← Older revision		Revision as of 08:49, 16 March 2023
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	=== Speed paired quad track ===		=== Speed paired quad track ===

	Speed paired quad track is one of the more common configurations that can be seen in real networks, particularly on longer stretches of quad track		Speed paired quad track is one of the more common configurations that can be seen in real networks, particularly on longer stretches of quad track. Some places where it can be seen include the UK (GWML, GEML, Brighton Main Line, MML), Germany (most of the (Siegburg-)Köln-Düsseldorf-Duisburg-Dortmund-Hannover corridor, Karlsruhe-Offenburg, Augsburg-München, ABS Nürnberg-Bamberg (under construction)), Finland (Helsink-Leppävaara and Helsinki-Kerava)

	It can be beneficial for creating simple junctions on one side of the line where only one of the track pairs needs to be able to branch off.		It can be beneficial for creating simple junctions on one side of the line where only one of the track pairs needs to be able to branch off.

	This advantage however only really exists for at grade junctions, for grade separated junctions, speed paired quad track will usually take up more space than direction paired. Also, if branching tracks join from either side of the main lines, extra bridges will be needed to avoid crossing the fast tracks. Furthermore, it is basically not possible for trains to easily go from the slow tracks to the fast tracks without creating a nightmare of path crossings or a complicated set of flyovers. For these reasons, the use of speed paired quad tracks should generally be avoided.		This advantage however only really exists for at grade junctions, for grade separated junctions, speed paired quad track will usually take up more space than direction paired (see for example. Also, if branching tracks join from either side of the main lines, extra bridges will be needed to avoid crossing the fast tracks. Furthermore, it is basically not possible for trains to easily go from the slow tracks to the fast tracks without creating a nightmare of path crossings or a complicated set of flyovers. For these reasons, the use of speed paired quad tracks should generally be avoided.

	FU-FD-SU-SD		FU-FD-SU-SD
Line 197:		Line 197:

	Outer slows allows branching off the slow lines more easily, stations can take less space, can be easier in some situations for noise isolation		Outer slows allows branching off the slow lines more easily, stations can take less space, can be easier in some situations for noise isolation

			{\| class="wikitable"
			\|+ Table of different quad track groupings
			\|-
			! Category !! Route paired !! Speed paired !! Direction paired (fast outer) !! Direction paired (fast inner)
			\|-
			\| Junction complexity vs capacity \|\| Poor unless routes are independent \|\| Poor unless at grade (still detrimental to capacity) \|\| Medium, favours joining fast tracks which can be problematic, easy for maximum capacity \|\| Good for grade separated junctions, favours joining slow tracks, easiest for maximum capacity
			\|-
			\| Support of different service patterns on a route \|\| Poor (behaves like 2 tracks) \|\| Mediocre (limited capacity to change between fast and slow tracks) \|\| Good (trains can easily change between fast and slow tracks) \|\| Good (trains can easily change between fast and slow tracks)
			\|-
			\| Ease of reversing trains \|\| Good, separated by route, low path conflicts for both pairs \|\| Good, low path conflicts for both pairs \|\| Medium, very good enroute (easy to have suburban or regional services stop and reverse), poor at major stations (usually requires flyovers for maximum capacity) \|\| Bad, only low path conflict reversing on fast tracks
			\|-
			\| Passenger usability \|\| Cross platform transfers at best one directional \|\| Cross platform transfers at best one directional \|\| Cross platform transfers possible between fast and slow tracks \|\| Cross platform transfers possible between fast and slow tracks
			\|-
			\| Station footprint \|\| Large \|\| Medium (requires platforms in between the tracks) \|\| Medium (requires platforms in between the tracks) \|\| Small (platforms between tracks not necessary for stops since they can be located on the slow tracks)
			\|}

	== Y junctions ==		== Y junctions ==

Qhfreddy: /* Speed paired quad track */

2023-03-16T04:16:50Z

Speed paired quad track

← Older revision		Revision as of 04:16, 16 March 2023
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	=== Speed paired quad track ===		=== Speed paired quad track ===

			Speed paired quad track is one of the more common configurations that can be seen in real networks, particularly on longer stretches of quad track

	~~Speed paired FU-FD-SU-SD~~		It can be beneficial for creating simple junctions on one side of the line where only one of the track pairs needs to be able to branch off.

			This advantage however only really exists for at grade junctions, for grade separated junctions, speed paired quad track will usually take up more space than direction paired. Also, if branching tracks join from either side of the main lines, extra bridges will be needed to avoid crossing the fast tracks. Furthermore, it is basically not possible for trains to easily go from the slow tracks to the fast tracks without creating a nightmare of path crossings or a complicated set of flyovers. For these reasons, the use of speed paired quad tracks should generally be avoided.

			FU-FD-SU-SD
	Places tracks next to each other		Places tracks next to each other

Qhfreddy: /* Route paired quad track */

2023-03-16T00:23:58Z

Route paired quad track

← Older revision		Revision as of 00:23, 16 March 2023
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	In the above example at Zwolle, the trains on one of the track pairs go up to Meppel, while the other track pair goes to Emmen. The trains to Emmen terminate at Zwolle and have their own platforms at the station there, so they don't interact at all with the trains taking the route to Meppel (which originate in the directions of Lelystad and Amersfoort).		In the above example at Zwolle, the trains on one of the track pairs go up to Meppel, while the other track pair goes to Emmen. The trains to Emmen terminate at Zwolle and have their own platforms at the station there, so they don't interact at all with the trains taking the route to Meppel (which originate in the directions of Lelystad and Amersfoort).

	Using route separated quad track is generally not recommended if trains need to weave between the two routes as it leads to many path conflicts that hurt capacity or necessitate the building of flyovers. Additionally, if there is a mix of slow and fast trains on the routes, the capacity of two double track routes is inferior to speed separated track where the fast trains have their dedicated track and the slow/stopping trains have theirs. However, as covered below in the section "[[~~https://wiki.nimbyrails.com/~~Track_layout_guide#Weaving_at_quad_track_entry\|Weaving at quad track entry]]", short sections of route separated quad track can be advantageous in some scenarios.		Using route separated quad track is generally not recommended if trains need to weave between the two routes as it leads to many path conflicts that hurt capacity or necessitate the building of flyovers. Additionally, if there is a mix of slow and fast trains on the routes, the capacity of two double track routes is inferior to speed separated track where the fast trains have their dedicated track and the slow/stopping trains have theirs. However, as covered below in the section "[[Track_layout_guide#Weaving_at_quad_track_entry\|Weaving at quad track entry]]", short sections of route separated quad track can be advantageous in some scenarios.

	=== Speed paired quad track ===		=== Speed paired quad track ===

Qhfreddy: /* Route paired quad track */

2023-03-16T00:23:36Z

Route paired quad track

← Older revision		Revision as of 00:23, 16 March 2023
Line 167:		Line 167:
	In the above example at Zwolle, the trains on one of the track pairs go up to Meppel, while the other track pair goes to Emmen. The trains to Emmen terminate at Zwolle and have their own platforms at the station there, so they don't interact at all with the trains taking the route to Meppel (which originate in the directions of Lelystad and Amersfoort).		In the above example at Zwolle, the trains on one of the track pairs go up to Meppel, while the other track pair goes to Emmen. The trains to Emmen terminate at Zwolle and have their own platforms at the station there, so they don't interact at all with the trains taking the route to Meppel (which originate in the directions of Lelystad and Amersfoort).

	Using route separated quad track is generally not recommended if trains need to weave between the two routes as it leads to many path conflicts that hurt capacity or necessitate the building of flyovers. Additionally, if there is a mix of slow and fast trains on the routes, the capacity of two double track routes is inferior to speed separated track where the fast trains have their dedicated track and the slow/stopping trains have theirs.		Using route separated quad track is generally not recommended if trains need to weave between the two routes as it leads to many path conflicts that hurt capacity or necessitate the building of flyovers. Additionally, if there is a mix of slow and fast trains on the routes, the capacity of two double track routes is inferior to speed separated track where the fast trains have their dedicated track and the slow/stopping trains have theirs. However, as covered below in the section "[[https://wiki.nimbyrails.com/Track_layout_guide#Weaving_at_quad_track_entry\|Weaving at quad track entry]]", short sections of route separated quad track can be advantageous in some scenarios.

	=== Speed paired quad track ===		=== Speed paired quad track ===

Qhfreddy: /* Quad track Y junctions */

2023-03-16T00:20:19Z

Quad track Y junctions

← Older revision		Revision as of 00:20, 16 March 2023
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	=== Quad track Y junctions ===		=== Quad track Y junctions ===

			==== Weaving at quad track entry ====

	As quad track lines typically operate at high frequencies, avoiding path crossings usually becomes paramount		As quad track lines typically operate at high frequencies, avoiding path crossings usually becomes paramount

Qhfreddy at 00:16, 16 March 2023

2023-03-16T00:16:10Z

← Older revision		Revision as of 00:16, 16 March 2023
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	== Fast-slow separation ==		== Fast-slow separation ==

			[[File:Route separation.jpg\|800px\|thumb\|right\|[https://www.openstreetmap.org/#map=16/52.5018/6.1275 Route separated track near Zwolle.] Note that the green line terminates and doesn't interact with the purple/pink lines on the other track pair.]]

	Usually when quad tracking lines, they are split into pairs of fast and slow lines, this ensures that speed conflicts are minimised		Usually when quad tracking lines, they are split into pairs of fast and slow lines, this ensures that speed conflicts are minimised
Line 159:		Line 161:
	A variety of different configurations can be used, each has their own advantages and disadvantages		A variety of different configurations can be used, each has their own advantages and disadvantages

	Route paired ~~1U-1D-2U-2D~~		=== Route paired quad track ===

			Route separated quad track track sections are essentially two independent double track routes. It can be of use where the quad section of quad track is short and/or the two routes are to be operated independently.

			In the above example at Zwolle, the trains on one of the track pairs go up to Meppel, while the other track pair goes to Emmen. The trains to Emmen terminate at Zwolle and have their own platforms at the station there, so they don't interact at all with the trains taking the route to Meppel (which originate in the directions of Lelystad and Amersfoort).

			Using route separated quad track is generally not recommended if trains need to weave between the two routes as it leads to many path conflicts that hurt capacity or necessitate the building of flyovers. Additionally, if there is a mix of slow and fast trains on the routes, the capacity of two double track routes is inferior to speed separated track where the fast trains have their dedicated track and the slow/stopping trains have theirs.

			=== Speed paired quad track ===

	~~Essentially two independent 2 track routes, not speed separated~~

	Speed paired FU-FD-SU-SD		Speed paired FU-FD-SU-SD

Qhfreddy: /* Examples of types of separation */

2023-03-08T19:14:01Z

Examples of types of separation

← Older revision		Revision as of 19:14, 8 March 2023
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	In the example in figure 3 there is a path conflict if we want the trains to use the junction at the same time. Using '''time separation''' the path conflict can be avoided, the trains will arrive at the junction at a different time.		In the example in figure 3 there is a path conflict if we want the trains to use the junction at the same time. Using '''time separation''' the path conflict can be avoided, the trains will arrive at the junction at a different time.

	In the example in figure 4 there is no path conflict, ~~because~~ the two trains are '''route separated''' .		In the example in figure 4 there is no path conflict as the paths do not cross, the two trains are therefore '''route separated'''.

	==== Examples of path conflicts ====		==== Examples of path conflicts ====

Qhfreddy: /* Fast-slow separation */

2023-03-08T19:03:54Z

Fast-slow separation

← Older revision		Revision as of 19:03, 8 March 2023
Line 170:		Line 170:

	Can require weaving junctions with relatively large footprint		Can require weaving junctions with relatively large footprint

			Impractical to allow trains to

	Direction paired		Direction paired

	FU-SU-SD-FD or SU-FU-FD-SD		FU-SU-SD-FD or SU-FU-FD-SD

			Allows easy transitioning between fast and slow lines, much increased flexibility in service patterns (intermediate speed services can stay on fast lines most of the time and be moved over to slow lines to stop at stations and be overtaken by fast services)

	Outer slows inner slows		Outer slows inner slows