Rail Diagrams

Topic moved from Test Forum by bevans on 01 Jun 2020 11:00
  WimbledonW Train Controller

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  bevans Site Admin

Location: Melbourne, Australia
Coming to you from the DAMS

  WimbledonW Train Controller

Location: Sydney
Coming to you from the DAMS

The above diagram shows the position of points, signals, and overlaps for a typical Simultaneous Arrival at Watermark, NSW,

Compared to a non-simultaneous arrival loop, the following changes are made.

* the overlaps are no longer minimal if non-existent; but are now quite long, say 200m or more.

* the yellow Down train and the green up trains can both enter the Loop and Main at the same time.

* the Arrival (Home) signals are at 51 or 52 points such as at Wallan, Vic, or 200m from the Departure (Starting) signal in NSW with a small overlap of about 110m depended on the position of the points.
* the standing room for the maximum length train (1350m) lies between the Departure Signal (6M and 6L or 7M and 7L) with the rear of the train "hanging out" by 236m at the opposite end, whereas in a non-SArr loop, the standing room is entirely between the opposing Departure signals, 6M-7M or 6L-7L.
* the Arrival signals in a SArr loop are 700m or 600m from the adjacent Departure signal namely 3-6M&6L, or 10-7M&7L.
* there is a 236m overlap past 6M-6L and past 7M-7L for trains entering the Main or Loop.
* there is a 700m/600m overlap past Arrival signals to opposing Departure signals 3-5M&6L or 10-7M&7L.

* there are some differences between NSW and Vic practices including
* VIC calls the signals Arrival and Departure
* NSW calls the same signals Home and Starting

* the 600m and 700m overlaps are arbitrary, and might be different for sighting reasons.
* the signals and points are numbered differently, with NSW being more inconsistent whereas VIC is more uniform.
* VIC signals are numbered:
** 2-Arrival                  3-points; 4 and 4U Departure
** 6 and 6U Departure, 7 points;            8 Arrival.

* In NSW down signals have odd numbers while up signals have even numbers. Points are numbered from 50.
* In VIC all CTC signals have even numbers while points have odd numbers.

At Wallan, because of a level crossing at Whittlesea Road, 2 signal and 4 signal are 137m apart.
  WimbledonW Train Controller

Location: Sydney


This is typical of loops on the NSW North Coast line; am not sure if the Main West, Main South, Main North, and Unanderra-Moss Vale are the same.

Things are different between Melbourne and Seymour, in Victoria.

Points to note:
* Numbering of signals on North Coast are different.
* Home signals are 200m from their respective Starting signals.
* 51 and 52 points are released by timing tracks:
** 120sec IIRC on main and loop 1350m for full length of Main or Loop
** 60 sec IIRC on 50m timing track approaching Starting signals.
* If you set Home signal 3 or 10 first, then opposing points 52 or 51 are set the other way to provide an overlap toward Starting signal.
* If you set Starting signal 6L/6M or 7L/7M, then both points can be set for a through move through Main or Loop.
* if Outer Home signals are provided, 1 or 2, then things are a bit different.
* loop lengths may be different.
  WimbledonW Train Controller

Location: Sydney
OVERLAPS versus CATCHPOINTS for Simultaneous Arrivals.

To allow simultaneous arrivals at Crossing Loops it is necessary to have either
* an overlap of perhaps 300m past the starting/departure signal;
* a catchpoint or run-off lead past the  starting/departure signal;
* an intermediate home signal protecting an overlap;
* some kind of ATP or ERTMS that regulates the speed of trains entering the crossing station on main or loop. No examples so far.

If Up and Down working is applicable you need two catchpoints past the respective Starting Signal
If Main and Loops working is applicable you may need four catchpoints.

Sometimes the catchpoint is implemented with a full lead, such as
* Thornleigh ETTT.
* Shellharbour Junction Up Loop

Crossing loops with U&D catchpoints include
* Albion Park.

Crossing loops with catchpoints in down direction and intermediate home signal and overlap in up direction
* Dapto

Crossing loops with catchpoints in both directions on Loop Line where there is no platform.
* Bombo

Crossing loops with overlaps in both directions allowing simultaneous arrivals include:
* Watermark
* Bells Gate
* Yarrawa
* Bylong ? - double length loop with intermediate signals and level xing in middle.

Other states are not so restrictive.

The Home/Arrival signal and preceding distant signal indications have a bearing on whether Sumultaneous Arrivals are possible. If they show Low Speed then No. If they show "medium" then maybe. In NSW a Low Speed guarantees that the Loop is unoccupied. In VIC the low speed does NOT guarantee that the Loop is unoccupied. Etc., etc.

In QLD, a home signal entering a main or loop with no overlap shows a Flashing Yellow which means no overlap.
In NSW, a flashing yellow has a contradictory meaning, namely next signal clear for straight or turnout.

For the sake of the argument it will be assumed that the Up train arrives first and takes the loop, while the Down train arrives second and takes the main. Also NSW nomenclature is used.

The Down train will not lose any time if the Up is locked away and stationary before the Down train sights the Down Distant signal showing Green from its sighting distance. In this case the Down Trains passes through the Main and loses no time because of the Cross. The Up train will then be able to resume its journey in the shortest possible time.

If the Up train doesn't enter the loop in time, and noting any low speed  loop points, then the Down train will receive a Yellow at the Down distance, and will have to reduce speed expecting to have to stop at the Down Home signal. Once the Up train is fully in the Loop, then the Down Train will find the Down Home and Down Starting signal both at Clear, and it can restart from a stationary position. Once the Down train has passed the Loop points at the Up end, the Up train can resume its journey, losing what ever time is lost because of low speed turnouts.

The higher the speed of the loop points the better.

Time is also lost recharging the air brakes on conventional trains. Electronically controlled pneumatic brakes (ECPB) on some trains improve braking performance. Acceleration and braking rates need to be adjusted for gradients and the empty or full state of the load. Speeds need to be adjusted for speed limits on plain lines and through points including trains lengths. Separate calculations need to be done for short passenger trains and long freight trains.

The equations of motion need to be applied to give numerical values to the movements. These include:
V^2 = U^2 +2.a.s .
s = (V^2 - U^2)/2.a
V = U + a.t
a = (V - U) / t
t = (V - U) / a

It goes without saying that calculating the passage time through crossing loops is complicated and needs to be done with a spreadsheet or a specialist program like MTRAIN.


In this case, the second train to arrive gets a medium aspect (Flashing Yellow) at the Down Distant, and a Caution aspect (Yellow) at the Down Home and is prepared to stop at the Down Starting Signal until the Up train is fully in the Loop, in which case the Starting Signal will clear. Once the rear of the Down train clears the clearance post near the points at the Up end, the Up train can proceed on its way though the low speed points.

The higher the speed of the loop points the better, especially for departing trains.

For equations of motion see https://en.wikipedia.org/wiki/Equations_of_motion


After 10 years of development ARTC and Lockheed Martin are about to commission their Advanced Train Management System (ATMS) in a big way. A trial section is between Port Augusta and Whyalla. ATMS replaces lineside signals with radio and satellite "virtual signals", with improved safety, speeds, and headways. Ability to regulate the speed of trains continuously at crossing loops, would probably make "simultaneous arrivals" available everywhere.  Signals are replaced by "Main Line Indicators" (MLI). Level Crossings are also controlled and supervised. See https://www.artc.com.au/projects/atms/

ATMS (Advanced Train Management System)

See 2012 [size=2]https://www.railpage.com.au:80/f-t11327619-0-asc-s75.htm[/size] ATMS
See 2014 https://www.railpage.com.au/f-p1901093.htm ATMS
See 2015 https://www.railpage.com.au/f-p1932580.htm TCMS
See 2015 [size=2]https://www.railpage.com.au/f-t11382084.htm[/size]  JH ETO
See 2020 [size=2]https://www.railpage.com.au/news/topic-40/[/size]  ATMS
See 2020 [color=#0e7744]http://www.railpage.com.au/news/s/rapid-adoption-of-atms-key-to-freight-rail-competitiveness[/color] ATMS

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