Simulation/Railways

generated on 2019-06-16 00:18:49.679326 from the wiki page for Simulation/Railways for SUMO git

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.

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 overlayed exactly. These edges are referred to as superposed (alternatively as bidirecticional 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 bidrectional track they will restrict it's usage to one direction at a time.

Bidirectional rails in SUMO-GUI

SUMO-GUI automatically shows only one of both edges to avoid duplicate drawing of cross-ties. The visualisation option show lane direction can be used to identifiy superposed edges. (arrows in both directions will be show).

Working with bidirectional tracks in NETEDIT

  • To show both edges that constitute a bidirectional track, activate edge visualisation otpion spread superposed. Both edges will be drawn narrower and with a side-offset to make them both visible without overlap.
  • 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

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. A large number of these issues can be fixed automatically be setting the NETCONVERT-option --railway.topology.repair. To analyze problems with bidirectional tracks, the option --railway.topology.output <FILE> can be used to identify problematic tracks. The option --railway.topology.all-bidi can be used to make all tracks usable in both directions.

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.

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.

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.

Modelling Trains

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

  • Freight
  • ICE1
  • ICE3
  • RB425
  • RB628
  • REDosto7
  • NGT400
  • NGT400_16

These types model traction and rolling resistance for particular trains. Alternatively, any other car following model may be used and configured with appropriate acceleration / deceleration parameters.

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.

Visualisation

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

  • carriageLength
  • locomotiveLength
  • carriageGap

Limitiations

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