Railways

Train Simulation#

This page describes simulations of trains in SUMO. To build an intermodal simulation scenario with trains, additional steps have to be taken in comparison to a plain vehicular simulation.

Building a network for train simulation#

Railways#

Railways can be imported from OSM. They can also be explicitly specified using the existing vClasses.

Parallel Tracks#

If a railway has parallel tracks, these must be modelled as distinct edge elements instead of a single edge with multiple "lanes".

OSM#

Types#

When importing from OSM the following railway types are distinguished by default (via <SUMO_HOME>/data/typemap/osmNetconvert.typ.xml):

Electrification#

Whenever a railway is electrified, the vClasses rail, rail_electric and rail_fast are permitted to drive there. Otherwise, only vClass rail is allowed.

Usage#

By loading the additional typemap <SUMO_HOME>/data/typemap/osmNetconvertRailUsage.typ.xml, additional usage information is exported for the edge types:

  • main
  • branch
  • industrial
  • military
  • test
  • tourism

This will lead to compound edge type ids such as railway.rail|usage.main.

Track numbers#

Local track numbers (mostly in train stations) are exported as edge parameter track_ref. These values are shown in the edge parameter dialog and can also be used for coloring (color by param, streetwise).

Bidirectional track usage#

In reality all tracks can be used in either direction if the need arises but many rails are used in only one direction most of the time. In SUMO, bidirectional track usage must be enabled explicitly. This simplifies routing as rails will only be used in their preferred direction most of the time.

Bidirectional track usage is modeled by two edges that have their geometries exactly reversed and using the attribute spreadType="center". This will result in lane geometries that are overlaid exactly. These edges are referred to as superposed (alternatively as bidirectional rail edges). In the .net.xml file these edges are marked with bidi="<REVERSE_EDGE_ID>" but this is a generated attribute and not to be set by the user.

When Rail signals are placed at both ends of a bidirectional track they will restrict it's usage to one direction at a time.

Bidirectional rails in sumo-gui#

Visualization of bidirectional tracks has a distinct style and dedicated settings.

Working with bidirectional tracks in netedit#

  • To show both edges that constitute a bidirectional track, activate edge visualization option spread bidirectional railways/roads (see visualization settings). Both edges will be drawn narrower and with a side-offset to make them both visible without overlap.
    • this is highly recommended when using connection mode to define connections among bidirectional tracks as it's otherwise hard to distinguish the affected edges
    • the pre-defined gui setting scheme 'rail' automatically activates the spread ... setting.
  • To find (and highlight) all bidirectional tracks, use attribute selection and search for attribute bidi with a value of 1
  • Create bidirectional tracks as explained here

Routing in bidirectional networks#

When train tracks can be used in both directions, there is considerable freedom for trains when search a path through the network. To reduce the number of conflicts (when two vehicles want to use the same track in opposite directions), the preferred direction for each track can be defined and factored into the routing decision.

To express this preference, the edges in the preferred direction and on the preferred side may be assigned a higher priority value. This value will be taken into account when setting option --weights.priority-factor FLOAT which applies to sumo and duarouter.

At the default option value of 0. Edge priority is ignored when routing. When setting a positive value, the edges with the lowest priority receive a penalty factor to their estimated travel time of 1 + FLOAT (where FLOAT is the option argument) whereas the edges with the highest priority receive no penalty. Edges with medium priority will receive a penalty of 1 + x * FLOAT where

  x = (edgePriority - minPriority) / (maxPriority - minPriority)

The priority values can either be assigned by the user or computed heuristically by netconvert as explained below.

Priority from partially restricted directionality#

If some of the tracks in the network are uni-directional these can be used to define the main direction and this property can be extroplated based on geometry (straightness) and topology (switches) onto the rest of the network This is done by setting the option --railway.topology.direction-priority. The assigned priority values are:

  • 4: unidirectional track
  • 3: main direction of bidirectional track
  • 2: undetermined main direction (straight continuation from different directions of unidirectional track)
  • 1: undetermined main direction (no continuation from unidirectional track)
  • 0: reverse of main direction of bidirectional track

Priority from partially defined values#

If some of the tracks in the network have priority values defined (by convention with the values 0 and 4) these can be used to define the main direction and this property can be extroplated based on geometry (straightness) and topology (switches) onto the rest of the network This is done by setting the option --railway.topology.extendn-priority. The assigned priority for the other network edges also range from 1 to 3 just as above.

Importing bidirectional tracks from OSM#

When importing networks from OSM, rails tagged with railway:preferred_direction:both are automatically imported as superposed edges.

Handling Problems in bidirectional railway networks#

Commonly, rail networks import from OSM are incomplete in regard to bidirectional track usage. One example would be terminal tracks which a train can only leave by reversing direction. netconvert provides several options to deal with this problem:

  • --railway.topology.output <FILE>: Identify problematic tracks (i.e. for manual correction).
  • --railway.topology.repair : Automatically fixes problems by analyzing rail network topology and adding bidirectional tracks
  • --railway.topology.repair.minimal : Apply automated fixes but only those which are needed for the operation loaded public transport lines
  • --railway.topology.repair.connect-straight : Allow bidirectional rail use wherever rails with opposite directions meet at a straight angle
  • --railway.topology.repair.stop-turn : Add turn-around connections at all loaded stops (to enable direction reversal).
  • --railway.topology.all-bidi : make all tracks usable in both directions.
  • --railway.topology.all-bidi.input-file : Load edge ids from text file and make those tracks usable in both directions. (one edge id per line, optionally prefixed with 'edge:' as in a selection file created with netedit).

Rail Signals#

The node type rail_signal may be used to define signals which implement Automatic Block Signaling.

By setting the netconvert-option --railway.signals.discard all signals can be removed from a network.

When working with bidirectional tracks, rail signals will affect both directions of travel by default. This can be changed in netedit.

Rail Crossings#

The node type rail_crossing may be used to define railway crossings. At these nodes trains will always have the right of way and road vehicles get a red light until there is a safe gap between approaching trains.

When importing networks from OpenStreetMap, rail crossings will be imported automatically. For other input data sources the crossings may have to be specified via additional xml files or set via netedit after importing.

Rail Crossing Parameters#

The following parameters may be defined in an additional file to configure timing and behavior of a rail crossing (example below). Time values are in seconds.

  • time-gap : time headway of approaching train that triggers closing the crossing (default 15)
  • space-gap : space headway of approaching train that triggers closing the crossing (default -1, which disables this check)
  • min-green-time : minimum green time for opening the crossing when another train is approaching (default 5)
  • opening-delay : time after train has passed the crossing before the opening sequence starts (default 3)
  • opening-time : time for opening the crossing (indicated by red-yellow state 'u') (default 3)
  • yellow-time : time for closing the crossing (default 3)

When setting parameters, id indicates the id of the rail-crossing junction and programID is always '0'.

<additional>
    <tlLogic id="C" programID="0">
        <param key="time-gap" value="15.0"/>
        <param key="space-gap" value="-1.0"/>
        <param key="min-green-time" value="5.0"/>
        <param key="opening-delay" value="3.0"/>
        <param key="opening-time" value="3.0"/>
        <param key="yellow-time" value="5.0"/>
    </tlLogic>
</additional>

Kilometrage (Mileage, Chainage)#

Edges support the attribute distance to denote the distance at the start of the edge relative to some point of reference for a linear referencing scheme. When the distance metric decreases along the forward direction of the edge, this is indicated by using a negative sign for the distance value.

The distance value along an edge is computed as:

  |edgeDistance + vehiclePos|

Edge distance is imported from OSM and can also be be set along a route in netedit

The distances value can be written in fcd-output using option --fcd-output.distance. It may then be used for plotting by plot_trajectories.py using the code k (i.e. -t kt). The distances can also be visualized in sumo-gui (color edges by distance).

Note

Negative distance values are not currently supported (pending introduction of another attribute)

Modelling Trains#

There is a dedicated carFollowMode for trains which can be activated by setting carFollowModel="Rail" trainType="<TYPE>" in the <vType> definition. Allowed values for trainType are

  • Freight
  • ICE1
  • ICE3
  • RB425
  • RB628
  • REDosto7
  • NGT400
  • NGT400_16
  • MireoPlusB
  • MireoPlusH
  • custom

These types model traction and rolling resistance for particular trains. To represent the behavior of arbitrary trains, the "custom" trainType may be used (see below). Alternatively, any other car following model may be used and configured with appropriate acceleration / deceleration parameters.

Custom dynamics model with tabular data#

The vType attributes speedTable, tractionTable and resistanceTable can be used to specify a custom interpolation table for traction and resistance. Each attribute is interpreted as a table column where the rows defines the traction and resistance for the corresponding speed. The speeds must be given in m/s whereas the traction and resistance forces are in kN. Intermediate values are obtained by linear interpolation.

Example:

    <vType id="0" vClass="rail" carFollowModel="Rail" trainType="custom"
           speedTable="0 2.78 5.56 8.33 11.11 13.89 16.67 19.44 22.22 25 27.78 30.56 33.33"
           tractionTable="300 300 263 179 135 108 90 77 67.5 60 54 49 45"
           resistanceTable="2 4 8.5 14 22 31 41.5 54 68 83.5 111 120 140"/>   

Custom dynamics model with parameterized curves#

The vType attributes maxPower and maxTraction can be used to specify the traction curve for a given speed (in m/s) according to the formula:

traction_kN = min(maxPower / speed, maxTraction

The vType attributes resCoef_quadratic, resCoef_linear and resCoef_constant can be usd to specify the resistance curve for a given speed (in m/s) according to the formula:

resistance_kN = resCoef_quadratic * speed * speed + resCoef_linear * speed + resCoef_constant

Example:

   <vType id="0" vClass="rail" carFollowModel="Rail" trainType="custom" maxPower="2350" maxTraction="150"
        resCoef_quadratic="0.00028" resCoef_linear="0.00003" resCoef_constant="1.670"/>

The attributes

Train Schedules#

Train schedules are defined in the same way as for any other type of public transport.

Generated by plotXMLAttributes.py.

Train Interaction#

When simulation trains on a network with railway signals, trains will only enter a block (a section of edges between signals) if it is free of other trains. When there are no rail signals or multiple trains have been inserted in the same block, they will automatically keep a safe distance according to their car following model. When using carFollowModel="Rail", trains will always keep enough distance to the leading train to come to a safe stop even if the lead train was to stop instantly.

Reversing Direction#

Trains will reverse direction if all of the following conditions are met:

  • The head of the train is on a normal edge (not on an intersection / railway switch)
  • The whole length of the train is located on rail-edges that allow bidirectional use.
  • The speed of the train is below 0.1m/s.
  • The train does not have any further stops on the current edge
  • The succeeding edges in the train's route are the reverse-direction edges of those it is currently on
  • There is a "turn-around" connection from the current train edge to the reverse direction edge

    Note

    When importing public transport stops with option --ptstop-output, all bidirectional edges with a public transport stop will have the necessary turn-around connection and thus be eligible for reversing.

Portion working#

Trains can be split and joined (divided and coupled) at stops. If a person or container travels in a train that is split or joined and wants to continue travelling in the new part, it requires a distinct <ride> or <transport> element in it's plan. No delay for boarding or loading will occur in the simulation for this.

Splitting a train#

To split a train, the following input definition can be used. The rear half of the train is defined as a new vehicle which depart value split. The train train that is being split must define the 'split' attribute in its stop definition referencing the id of the rear half.

   <vType id="train" vClass="rail"/>
    <vType id="splitTrain" vClass="rail" length="50"/>
    <trip id="t0" type="train" depart="0.00" from="a" to="c">
        <stop busStop="B" duration="60.00" split="t1"/>
    </trip>
    <trip id="t1" type="splitTrain" depart="split" from="b" to="e">
        <stop busStop="B" duration="60.00"/>
    </trip>

When defined this way, The rear part of the train will be created as a new simulation vehicle once the first part has reached the stop. After stopping, The front half of the train will continue with reduced length. If the vehicle that is split if (with depart="split") uses attribute departPos="splitFront" it will instead be inserted at front and the part that keeps it's id will be positioned in the rear.

Joining two trains#

To join two trains, they have to stop at in close proximity (i.e. at the same <busStop> or <trainStop>) and then one of them is removed (referred to as the joining train) and the other made longer (referred to as the continuing train.

The continuing train requires a stop with attribute triggered="join". By default this train will only continue it's route after another train has joined with it and wait indefinitely for this condition. However, by setting stop attribute extension, waiting for the trigger condition can be aborted (as for any other condition). The joining train requires a stop with attribute join="VEH_ID" where VEH_ID denotes the id of the continuing train.

The joining operating consists of having the joining train arrive and disappear from the simulation and the continuing train to be made longer according to the length of the joining train. The following conditions must be met for the joining operation to take place:

  • the continuing train has fulfilled its stopping duration (defined by attributes duration and until)
  • the trains are in close proximity in either of the two ways:
    • the continuing train has it's back is on the same lane as the joining train and the gap between them is less than the minGap of the joining train +1m
    • the joining train has it's back on the same lane as the continuing train and the gap between the trains is less the minGap of the continuing train +1m

The following is an example definition for joining two trains:

    <vType id="train" vClass="rail"/>
    <vType id="splitTrain" vClass="rail" length="50"/>
    <trip id="t0" type="splitTrain" depart="0.00" from="a" to="c">
        <stop busStop="B" duration="60.00" triggered="join"/>
    </trip>
    <trip id="t1" type="splitTrain" depart="30" from="d" to="b">
        <stop busStop="B" duration="5.00" join="t0"/>
    </trip>

Caution

if the joined train is in the front and covers multiple edges, then these must all match the route of the continuing train. Also the joining train should have the join-stop on the last edge of it's route.

Rail Signal Behavior#

Rail signals perform the following safety functions automatically

  • a) guard the track up to the next rail signal (signal block) so that only one train can enter this section at a time. This prevents rear-end collisions.
  • b) guard the track so that vehicles from different branches (flanks) cannot enter the same section. This prevents flanking collisions.
  • c) guard the track so that vehicles cannot enter bidirectional sections at the same time. This prevents head-on collisions.
  • d) prevent deadlocks on bidirectional sections

Functionality a) corresponds to the "classic" safety behavior of rail signals (PZB). When option --railsignal-moving-block is set or individual signals are configured with parameter moving-block (see below), feature a) is disabled and trains will use their configured carFollowModel (i.e. 'Rail') for distance keeping. This is similar to the LZB safety system when used with extremely short virtual blocks.

To switch a single signal into moving-block-mode, the following additional file may be loaded:

<additional xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://sumo.dlr.de/xsd/additional_file.xsd">
    <tlLogic id="gneJ8" programID="0">
        <param key="moving-block" value="true"/>
    </tlLogic>
</additional>

Parameter moving-block may also be updated at runtime with traci.trafficlight.setParameter.

Schedule Constraints#

Additionally, rail signals can enforce train ordering to ensure that a scheduled order at stations can be kept. To make use of this, the following elements can be loaded from an additional file:

   <railSignalConstraints id="A">
        <predecessor tripId="t0" tl="D" foes="t1" limit="2"/>
        <predecessor tripId="t0" tl="C" foes="t2"/>
        <insertionPredecessor tripId="t3" tl="E" foes="t4"/>
    </railSignalConstraints>

predecessor constraint#

This constrain defines that a given vehicle id (or tripId) can only pass the current signal after some other vehicle ('foe') with the given id or tripId has passed signal 'tl'. The foe vehicle must have been the last vehicle to do so or it must have been one of the last 'limit' vehicles at the time of switching green.

insertionPredecessor constraint#

This constrain defines that a given vehicle id (or tripId) can only be inserted on the block leading up to the current signal after some other vehicle ('foe') with the given id or tripId has passed signal 'tl'. The foe vehicle must have been the last vehicle to do so or it must have been one of the last 'limit' vehicles at the time of switching green.

Constraint Attributes#

Attribute Name Value Type Description
tripId id (string) The 'tripId' param of a vehicle or the id of a vehicle to which this constraint applies
tl id (string) The id of a railSignal
foes ids (string list) The ids of one or more vehicles that must have passed tl before the parent rail signal permits tripID to pass
limit int The number of intermediate vehicles that may pass tl after the foes before the constraint is evaluated for tripId. default: number of given foes. (setting a high number has now downside besides memory use but setting a low number may cause the constraint to block tripId indefinitely because the ids of the passed foes were overwritten by later trains)
active bool Whether this constraint is active (inactive constraints may still be retrieved via TraCI)

constraints generation#

Constraints can be generated using the tool generateRailSignalConstraints.py by using a route file with stops that define a schedule.

TraCI#

Rail signals and rail crossings can be controlled with function traci.trafficlight.setRedYellowGreenState. They can also be switched off with traci.trafficlight.setProgram(tlsID, "off"). In either case, normal operations can be resumed by reactivating the default program "0": traci.trafficlight.setProgram(tlsID, "0").

Trains can be controlled just like cars by using the traci.vehicle functions. Furthermore the following functions are available for rail signals:

  • traci.trafficlight.getBlockingVehicles(tlsID, linkIndex): Returns the list of vehicles that are blocking the subsequent block for the given tls-linkIndex from the perspective of the closest vehicle upstream of the signal
  • traci.trafficlight.getRivalVehicles(tlsID, linkIndex): Returns the list of vehicles that also wish to enter the subsequent block for the given tls-linkIndex (regardless of priority) from the perspective of the closest vehicle upstream of the signal
  • traci.trafficlight.getPriorityVehicles(tlsID, linkIndex): Returns the list of vehicles that also wish to enter the subsequent block for the given tls-linkIndex (only those with higher priority) from the perspective of the closest vehicle upstream of the signal

Constraints#

Constraints can be queried and modified via TraCI:

  • getConstraints(tlsID, tripId=""): Returns the list of rail signal constraints for the given rail signal. If tripId is not "", only constraints with the given tripId are returned. Otherwise, all constraints are returned
  • getConstraintsByFoe(foeSignal, foeId=""): Returns the list of rail signal constraints that have the given rail signal id as their foeSignal. If foeId is not "", only constraints with the given foeId are returned. Otherwise, all constraints are returned
  • addConstraint(tlsID, tripId, foeSignal, foeId, type=0, limit=0): add constraint with the given values (type 0 is a predecessor constraint, 1 insertion predecessor, 2 foe insertion, ...)
  • swapConstraints(tlsID, tripId, foeSignal, foeId): Reverse the given constraint and return list of new constraints that were created (by swapping) to avoid deadlock.
  • removeConstraints(tlsID, tripId, foeSignal, foeId): remove constraints with the given values. Any combination of inputs may be set to "" to act as a wildcard filter """
  • updateConstraints(vehID, tripId=""): remove any constraints related to the given tripId if the vehicle with the given vehID no longer passes the respective rail signals (i.e. after rerouting).
    • if tripId is the empty string, the current tripId param of the vehicle is used
    • if the tripId would have changed in the part of the route affected by rerouting, the function must be called once for each individual tripId involved.

Visualization#

Trains#

The length of railway carriages, locomotive and the gap between the carriages can be configured using the following generic vType parameters:

  • locomotiveLength
  • carriageLength
  • carriageGap
  • carriageImages

These parameters control the appearance of trains in sumo-gui when drawing vehicles with the style 'simple shapes'. By default, the front of the train will be indicated by a darker carriage color and a front windscreen. This can be disabled by setting locomotiveLength="0". The parameter carriageImages accepts a comma-separated list of image file names to enable distinct images when using vehicle style 'raster images'.

Network#

By default, railway tracks are shown in sumo-gui in a distinct style:

  • tracks and crossties are rendered instead of filled shapes when zoomed in (configurable with visualization setting show rails)
  • turning arrows are not shown
  • the white bar that indicates right of way is not drawn
  • junction shapes are not shown and the internal edges that make up a railway switch are always visible (can be changed setting junction coloring to any scheme other than uniform)
  • traffic light (rail signal) indicators are drawn with an offset to the right to indicate the direction in which the signal is applied
  • for each pair of edges that make up a bidirectional track, only of is drawn to avoid artifacts. To make both edges visible (i.e. for selecting or otherwise interacting with that edge), the visualization setting spread bidirectional railways/roads in the Streets tab can be activated
  • the pre-defined gui setting scheme "Rail" can be used to activate the following settings that are helpful for diagnosing a railway simulation
    • spread bidirectional railways/roads
    • coloring junctions by type (making rail signals more visible)
    • constant junction size (making rail signals bigger when zoomed out)
    • show lane direction (direction is otherwise hard to judge for uni-directional tracks)
    • vehicles are shown as simple shapes to ensure articulated train shapes follow curves

Abstract Networks#

Road networks are most often modelled according to their actual layout in cartesian space. Such networks have all distances and angles in the same proportions as those of geographical map.

In the railway domain it is often useful to work with schematic (also called abstract) networks instead of (or in addition to) geographical networks. Such abstract networks can make it easier so see all tracks and switches on a single screen without zooming and panning. SUMO supports working with abstract maps in the following ways:

  • all roads and tracks can have a custom "length" value that differs from their visual length. This allows to separate the visualization of the network from it's simulation behavior (w.r.t. distance traveled).
  • sumo-gui supports loading an abstract map of a network along with a geographical map by using options -n geo.net.xml -N abstract.net.xml. The two networks must have the exact same topology and may only differ in their geometry.
    • The user may switch between the visualization of either geometry via the hotkey CTRL+K or by setting Street visualization setting secondary shape.
    • All outputs that include geometry information (i.e. fcd-output) will be according the the network loaded with option -n
  • the tool abstractRail.py can be used to convert geographic rail networks in abstract rail networks

Miscellaneous#

Limitations#

  • Individual rail cars / coupling / uncoupling cannot currently be modeled