• ScenarioGuide

Introduction#

This Tutorial is meant to serve as a high-level guide for building a sumo scenario. It provides an outline of the typical steps followed when building a scenario and lists the recommended documentation pages for each step.

Build the road network#

Every simulation requires a road network. The application netconvert is used to create a network which can be used by the simulation sumo. It is also possible to build/modify a simulation network by hand with use of netedit, which provides a graphical user interface.

If you already have some network data#

Check whether a direct import is possible: Networks/Import. Otherwise, you will need to convert the data to a simple XML-format which can be read by netconvert. Read this page: Networks/Import.

If you do not yet have any network data#

Use publicly available network data from OpenStreetMap as described here: Networks/Import/OpenStreetMapDownload. Then import the network as described here: Networks/Import/OpenStreetMap.

Generate the traffic#

First, you should understand the basics of vehicle modelling: Definition_of_Vehicles,_Vehicle_Types,_and_Routes. There are various ways to insert vehicles into the map. Your choice basically depends on what kind of information about the traffic you have: Demand/Introduction_to_demand_modelling_in_SUMO.

Improve your Scenario#

Most methods for network imports lead to deficiencies in network quality. These often manifest as unexpected/unrealistic traffic jams and teleporting vehicle errors.

Modifying the Network#

You will have to patch your network data to add missing roads, prohibit some turns, correct the number of lanes and add/remove some traffic lights. The recommended ways to perform the necessary changes include:

1. Encode the changes in plain-xml files as described in Networks/Building_Networks_from_own_XML-descriptions. Most XML-attributes are optional so you only need to set the values that you would like to change.
2. Patch your network using netconvert by loading the net.xml along with the plain-xml files. You can even use this during the initial import (i.e. load an OSM-file along with your plain-xml files)
3. Directly adjust your network with GUI: after opening the program netedit you first load the network file (*.net.xml) that needs to be modified. Then, you choose the respective functions in netedit to modify e.g. the number of lanes, road shapes, traffic signal plans, intersection geometries, and to combine intersections or edges.
4. Get new information from a updated network (e.g. osm) by using Net/netDiff.py. You can then use netconvert and the difference files generated by netDiff.py to update your network.

Example: Patching the type of a node#

prepare a file like this:

patch.nod.xml :

<nodes>
    <node id="id_of_the_node_you_want_to_modify" type="right_before_left"/>
<nodes>

and patch the network like this:

netconvert --sumo-net-file your.net.xml --node-files patch.nod.xml -o yourpatched.net.xml

or perform the patch during the initial import:

netconvert --osm-file yourOSMfile.xml --node-files patch.nod.xml ...<other options>

Modifying an imported network via plain.xml#

Instead of patching individual elements, you can also convert your network to plain.xml, modify the plain file and then re-assemble the network like this:

netconvert --sumo-net-file your.net.xml --plain-output-prefix yourplain

or during import:

netconvert --osm-files yourOSMinput.xml --plain-output-prefix yourplain ... <your other options>

This will give you the files:

yourplain.edg.xml
yourplain.nod.xml
yourplain.con.xml
yourplain.tll.xml

You can edit these files and then reassemble the network by loading some or all of them:

netconvert --edge-files yourplain.edg.xml --node-files yourplain.nod.xml -o new.net.xml

or

netconvert --edge-files yourplain.edg.xml --node-files yourplain.nod.xml --connection-files yourplain.con.xml -o new.net.xml

Modifying node positions with the help of sumolib#

Sumolib is a python library for working with SUMO files. The file <SUMO_HOME>/tests/tools/sumolib/patch_network/runner.py provides an example for randomly changing all node positions with a few lines of python code.

Traffic Light Programs#

In almost all cases, the traffic light programs will have been guessed by netconvert and turn out different from the real traffic lights. A simple way to improve traffic lights programs is making them start their program cycles at a different times. Experiment with the option --tls.half-offset and all the other --tls.* options of netconvert.

A more practical and efficient way to improve your traffic lights is to give the program explicitly with a tls.xml file.

As of now, netconvert only supports the creation of static traffic light programs. For dynamic traffic lights see Tutorials/TraCI4Traffic_Lights. Furthermore, actuated traffic control can also be set, either based on time gaps or time loss. More information about actuated traffic control and settings can be found at Simulation/Traffic_Lights#Actuated_Traffic_Lights).

Manage Scenarios#

If you have two networks A.net.xml and B.net.xml you may wish to find out how they differ. This can be accomplished using the tool <SUMO_HOME>/tools/net/netdiff.py. Running this tool will give you a set of plain-XML difference files. They only contain the differences grouped by deleted, created and changed elements. It is even possible to load these files along with A.net.xml to recreate B.net.xml.