Dev:Railway switch

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Introduction

The purpose of this example is twofold. It shall teach newcomers principles of modelling topologies with railML® 3. As for the proficient users, this tutorial is to provide a common way to describe a railway switch, e.g. for certification purposes.

A switch is a unit of a railway track network used to direct vehicles from one track to another track.

To separate the description of the infrastructure topology from its construction, railML® 3 is based on a connexity graph that is based on the structure of the RailTopoModel® . In the context of the description of a railway switch, this means that the type of railway switch (e.g., ordinary, or inside curved switch, etc.) is specified in the functional layer, while the location and mode of operation are specified in the topological layer. Please refer to “Example data” of the railML.org e.V. website for an example of a linear positioning system definition. Below code snippet below deliberately misses these for the sake of space reasons (this section is already very-very long). 

1  <?xml version="1.0" encoding="UTF-8"?>
2  <railML xmlns="https://www.railml.org/schemas/3.1"
3          xmlns:dc="http://purl.org/dc/elements/1.1/"
4          xmlns:gml="http://www.opengis.net/gml/3.2/"
5          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
6          xsi:schemaLocation="https://www.railml.org/schemas/3.1 https://www.railml.org/schemas/3.1/railml3.xsd"
7          version="3.1">
8    <infrastructure id="is_01">
9      <topology>
10       <netElements>
11         <netElement id="ne_b01"
12                     length="500.0">
13           <associatedPositioningSystem id="ne_b01_aps01">
14             <intrinsicCoordinate id="ne_b01_aps01_ic01"
15                                  intrinsicCoord="0">
16               <linearCoordinate positioningSystemRef="lps01"
17                                 measure="4500.0"/>
18             </intrinsicCoordinate>
19             <intrinsicCoordinate id="ne_b01_aps01_ic02"
20                                  intrinsicCoord="1">
21               <linearCoordinate positioningSystemRef="lps01"
22                                 measure="5000.0"/>
23             </intrinsicCoordinate>
24           </associatedPositioningSystem>
25         </netElement>
26         <netElement id="ne_b03"
27                     length="200.0">
28           <associatedPositioningSystem id="ne_b03_aps01">
29             <intrinsicCoordinate id="ne_b03_aps01_ic01"
30                                  intrinsicCoord="0">
31               <linearCoordinate positioningSystemRef="lps01"
32                                 measure="4300.0"/>
33             </intrinsicCoordinate>
34             <intrinsicCoordinate id="ne_b03_aps01_ic02"
35                                  intrinsicCoord="1">
36               <linearCoordinate positioningSystemRef="lps01"
37                                 measure="4500.0"/>
38             </intrinsicCoordinate>
39           </associatedPositioningSystem>
40         </netElement>
41         <netElement id="ne_b04"
42                     length="50.0">
43           <associatedPositioningSystem id="ne_b04_aps01">
44             <intrinsicCoordinate id="ne_b04_aps01_ic01"
45                                  intrinsicCoord="0">
46               <linearCoordinate positioningSystemRef="lps01"
47                                 measure="4500.0"/>
48             </intrinsicCoordinate>
49             <intrinsicCoordinate id="ne_b04_aps01_ic02"
50                                  intrinsicCoord="1">
51               <linearCoordinate positioningSystemRef="lps01"
52                                 measure="4550.0"/>
53             </intrinsicCoordinate>
54           </associatedPositioningSystem>
55         </netElement>
56       </netElements>
57       <netRelations>
58         <netRelation id="nr_b01b03"
59                      positionOnA="0"
60                      positionOnB="1"
61                      navigability="Both">
62           <elementA ref="ne_b01"/>
63           <elementB ref="ne_b03"/>
64         </netRelation>
65         <netRelation id="nr_b01b04"
66                      positionOnA="0"
67                      positionOnB="0"
68                      navigability="None">
69           <elementA ref="ne_b01"/>
70           <elementB ref="ne_b04"/>
71         </netRelation>
72         <netRelation id="nr_b03b04"
73                      positionOnA="1"
74                      positionOnB="0"
75                      navigability="Both">
76           <elementA ref="ne_b03"/>
77           <elementB ref="ne_b04"/>
78         </netRelation>
79       </netRelations>

80     <networks>
82       <network id="nw01">
83         <level id="lv0"
84                descriptionLevel="Micro">
85           <networkResource ref="ne_b01"/>
86           <networkResource ref="ne_b03"/>
87           <networkResource ref="ne_b04"/>
88           <networkResource ref="nr_b01b03"/>
89           <networkResource ref="nr_b01b04"/>
90           <networkResource ref="nr_b03b04"/>
91         </level>
92       </network>
93     </networks>
94   </topology>
95   <functionalInfrastructure>
96     <switchesIS>
97       <switchIS id="swi02"
98                 continueCourse="left"
99                 branchCourse="right"
100                type="ordinarySwitch">
101        <name name="69W03"
102              language="en"/>
103        <spotLocation id="swi02_sloc01"
104                      netElementRef="ne_b03"
105                      applicationDirection="normal"
106                      pos="200.0">
107          <linearCoordinate positioningSystemRef="lps01"
108                            measure="4.500"/>
109        </spotLocation>
110        <leftBranch netRelationRef="nr_b01b03"
111                    branchingSpeed="80"
112                    joiningSpeed="80"
113                    radius="0"/>
114        <rightBranch netRelationRef="nr_b03b04"
115                     branchingSpeed="40"
116                     joiningSpeed="40"
117                     radius="300"/>
118      </switchIS>
119    </switchesIS>
120    <tracks>
121      <track id="trc03"
122             type="mainTrack">
123        <linearLocation id="trc03_lloc01"
124                        applicationDirection="both">
125          <associatedNetElement netElementRef="ne_b03"
126                                keepsOrientation="true"
127                                posBegin="0.0"
128                                posEnd="200.0">
129                </associatedNetElement>
130        </linearLocation>
131        <trackEnd ref="swi02"/>
132        <length value="200.0"
133                type="physical"/>
134      </track>
135      <track id="trc04"
136             type="mainTrack">
137        <name name="2"
138              language="en"/>
139        <linearLocation id="trc04_lloc01"
140                        applicationDirection="both">
141          <associatedNetElement netElementRef="ne_b01"
142                                keepsOrientation="true"
143                                posBegin="0.0"
144                                posEnd="500.0">
145                </associatedNetElement>
146        </linearLocation>
147        <trackBegin ref="swi02"/>
148        <length type="physical"
149                value="500.0"/>
150      </track>
151      <track id="trc07"
152             type="connectingTrack">
153        <linearLocation id="trc07_lloc01"
154                        applicationDirection="both">
155          <associatedNetElement netElementRef="ne_b04"
156                                keepsOrientation="true"
157                                posBegin="0.0"
158                                posEnd="50.0">
159                </associatedNetElement>
160        </linearLocation>
161        <trackBegin ref="swi02"/>
162        <length value="50.0"
163                type="physical"/>
164      </track>
165    </tracks>
166  </functionalInfrastructure>
167</infrastructure>
168</railML>


Topological layer of a switch

To describe the railway switch at the topological level, at least three elements must be defined (ellipses). The “branching” course needs to be described, from track 3 to track 7 in the example and the “continuing” direction needs to be modelled, from track 3 to track 4 in the example. On a topological level this description is performed using <netElement> (lines 10-56 of the listing). These elements are linked by relations (Figure 1: green and red circles; lines 57-80 of the listing).

Representation of the railway switch in railML® 3

In railML® 3, the mechanism for being able to travel from one element to another is called connexity representation and is implemented using relations with a navigability attribute (in the The RailTopoModel® Wiki). The condensed relations matrix for this case is presented in Table.

3 4 7
3 + +
4 + -
7 + -

In the table, pluses are navigable relations (e.g., line 61 of the listing). The train can go through the railway switch in a “branching” direction ‒ from track 3 to track 7 ‒ and in “continuing” direction ‒ from track 3 to track 4. In this case, an ordinary switch is described, so the @navigability attribute is set to “both”. In other cases where only unidirectional travel is allowed the other enumeration values “AB” and “BA” may be used to describe the permitted orientation of travel.

To represent the impossibility to go from track 4 to track 7 directly, non-navigable relations (attribute @navigability, line 68 of the listing) are used ‒ they are represented as minuses in Table 1.

Functional layer of a switch

Figure 2 - Possible orientations of a railway switch

The @continueCourse and @branchCourse attributes represent the direction of movement through the railway switch (Figure 2, line 98 of the listing). Please note that two directions are present on the figure. Application direction is not relevant for specifying the direction using @continueCourse and @branchCourse. The directions are always meant looking from switch beginning to switch end. However, the application direction is imperative for understanding the orientation of a switch.

The description of all cases is presented in Table 2. The case of Figure 2 is a). See the changes in source code below.

Table 2 Direction of the railway switch construction in railML® 3

Case @continueCourse @branchCourse @applicationDirection
a left right normal
b left right reverse
c right left normal
d right left reverse

A switch in railML® is defined as a non-linear infrastructure element (although it is possible to describe it by area location. We will provide this example as soon as possible). As such its position is defined by one or more <spotLocation>-s. In contrast a track is defined as a linear infrastructure element, accordingly its position is specified using a <linearLocation>.

Based on the topology of the example above, the child element <spotLocation> defines the logical position of the railway switch (line 103 of the listing) to be at the end of the <netElement> b03 (@position is given with 200 and the length of the <netElement> is specified as 200 as well). Track 3 is also located at element b03 (line 125 of the listing). This implies that switch is located at track.

It is recommended that switch is located at the net element of the beginning of a switch, i.e. b03. It is not recommended to set elements b01 or b04 as spot location of a switch.

The railway switch is then connected to navigable relations via <leftBranch> and <rightBranch> children (line 110 of the listing). Railway switches are not explicitly linked with non-navigable relations (line 65 of the listing). This means that both navigable and non-navigable relations are necessary to describe topology of an ordinary railway switch but only first ones are linked to a switch by @netRelationRef attributes of a switch’s children.

See source code for case b) below: 

<switchIS id="swi02"
          continueCourse="left"
          branchCourse="right"
          type="ordinarySwitch">
    <name name="69W03"
          language="en"/>
    <spotLocation id="swi02_sloc01"
                  netElementRef="ne_b03"
                  applicationDirection="reverse"
                  pos="200.0">
        <linearCoordinate positioningSystemRef="lps01"
                          measure="4.500"/>
    </spotLocation>
    <leftBranch netRelationRef="nr_b01b03"
                branchingSpeed="80"
                joiningSpeed="80"
                radius="0"/>
    <rightBranch netRelationRef="nr_b03b04"
                 branchingSpeed="40"
                 joiningSpeed="40"
                 radius="300"/>
</switchIS>

See source code for case c) below: 

<switchIS id="swi02"
          continueCourse="right"
          branchCourse="left"
          type="ordinarySwitch">
    <name name="69W03"
          language="en"/>
    <spotLocation id="swi02_sloc01"
                  netElementRef="ne_b03"
                  applicationDirection="normal"
                  pos="200.0">
        <linearCoordinate positioningSystemRef="lps01"
                          measure="4.500"/>
    </spotLocation>
    <rightBranch netRelationRef="nr_b01b03"
                branchingSpeed="80"
                joiningSpeed="80"
                radius="0"/>
    <leftBranch netRelationRef="nr_b03b04"
                 branchingSpeed="40"
                 joiningSpeed="40"
                 radius="-300"/>
</switchIS>

See source code for case d) below: 

<switchIS id="swi02"
          continueCourse="right"
          branchCourse="left"
          type="ordinarySwitch">
    <name name="69W03"
          language="en"/>
    <spotLocation id="swi02_sloc01"
                  netElementRef="ne_b03"
                  applicationDirection="reverse"
                  pos="200.0">
        <linearCoordinate positioningSystemRef="lps01"
                          measure="4.500"/>
    </spotLocation>
    <rightBranch netRelationRef="nr_b01b03"
                branchingSpeed="80"
                joiningSpeed="80"
                radius="0"/>
    <leftBranch netRelationRef="nr_b03b04"
                 branchingSpeed="40"
                 joiningSpeed="40"
                 radius="-300"/>
</switchIS>

Curve of a switch

UnderConstruction.png This page is under construction since July 26th 2024. Task: Finalize modeling. Sorry for temporary problems. See the discussion page to find a summary of the tasks and to coordinate the work on this page. Recognize that the content of this page may change quickly. railML Coord Infrastructure (talk) 11:37, 26 May 2025 (CET)


🗒️ This is a draft.  

Railway switch consists of a switch, connecting rails and a frog. Connecting rail set of an ordinary switch consists of two straight and curved rails. Curved rails have some radius. This curve is called a switch curve.

Railway switch curve

In the railML® 3 model it is possible to represent radius of each branch of the railway switch. Negative and positive values have corresponding meaning defined as in the <horizontalCurve>/@radius attribute.

Below you can see some of railway switch @types (for context see OSJD guide [1] in Russian and TU Dresden guide [2] in German). Inside curved and outside curved switches are presented in their usual location in the schematic track plan.

Depending on the orientation an ordinary railway switch has positive or negative value of @radius of <rightBranch> or <leftBranch>.

Both <rightBranch> and <leftBranch> of inside curved switch should have positive or negative value.

<rightBranch> and <leftBranch> of outside curved switch should have positive and negative value.

See concrete examples in table below, source code at dev:Railway switch guide.

Case leftBranch/@radius rightBranch/@radius
Ordinary switch a) 0 300
Ordinary switch b) 0 300
Ordinary switch c) -300 0
Ordinary switch d) -300 0
Inside curved switch a) 300 400
Inside curved switch b) 300 400
Outside curved switch -300 300

Remarks

See <switchIL> for interlocking context.

Comparison with railML 2

Please refer to Differences_between_railML2_and_railML3.

References

  1. ↑ https://osjd.org/api/media/resources/1528909?action=download (external link)
  2. ↑ https://tu-dresden.de/bu/verkehr/ibv/schienenfahrwege/ressourcen/dateien/download_gvb/lehrmaterialien/Aufbau_V/A-09-Bogenweichen.pdf (external link)
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