Tutorials/Driving in Circles

In this tutorial we will build a simple circular net with netedit and use rerouters to make vehicles drive in circles. All definition files can also be found in the <SUMO_HOME>/docs/tutorial/circles directory.

Build a network#

First open netedit and create edges to form a closed loop. To do that press Ctrl-N to create a new network and then press e to enter the edge editing mode. Now create a closed loop of edges (you might consider to check 'chain' just right from the edit-mode selection, see figure).


The result should look more or less like shown in the figure. The important thing is the circular shape. Now save the network somewhere (Ctrl-Shift-S) in an empty directory (we will refer to that place by baseDir). As name for the created net-file type in circles.net.xml.

Create vehicles and run SUMO#

In the baseDir create two empty text-files, call them circles.rou.xml and circles.sumocfg. These files will define our vehicles and the run configuration.

First, we edit circles.rou.xml and define a vehicle flow of five standard passenger cars. The file contents should look like this:

   <vType id="car" type="passenger" length="5" accel="3.5" decel="2.2" sigma="1.0"/>
   <flow id="carflow" type="car" beg="0" end="0" number="5"/>

For further explanation of how to define flows and vTypes see the respective Wiki-pages: Flow Definitions and Vehicle Types.

To use the route-file and the generated net-file with SUMO, we edit the configuration-file circles.sumocfg to tell SUMO where it finds vehicle and net definitions:

       <net-file value="circles.net.xml"/>
       <route-files value="circles.rou.xml"/>


First attempt to run the simulation

Now let us try to start sumo with the config that we have just created. To do so either double-click on the configuration-file circles.sumocfg (under Windows, if your installation was done with default settings) or change to the baseDir in a terminal and start sumo (with graphical user interface) there by typing sumo -c circles.sumocfg. (If this does not start sumo, you might have to add the SUMO/bin directory to your PATH?)

Did it work? No.

Let us have a look at the Message Window at the bottom of the GUI to endeavor what went wrong (by the way: the Message Window is often a very useful resource for information for setting up a simulation take a look at it first, if you run into problems).

It says: Error: The route for flow 'carflow' has no edges. This means that SUMO does not know from where to where the vehicles of the flow we declared in circles.rou.xml should take. To do this, we need to add attributes to and from, and provide corresponding edge-ids to the flow.


Renaming an edge in netedit

The edge-ids can be inspected and modified in netedit: open your network-file circles.net.xml and press i to enter the inspect-mode. Left-click on an arbitrary edge and rename it to edge1. Left-click on a different edge and rename it to edge2. Then save your network (Ctrl-S).

Now we add the from-edge and the to-edge to the flow in circles.rou.xml:

    <flow id="carflow" type="car" beg="0" end="0" number="5" from="edge1" to="edge2"/>


Running five cars on the circular net

Let's try to run SUMO again. The window should now show the network you have created before in netedit and you can start the simulation by clicking on the play button (Image:play.gif) or the step button (Image:step.gif). If you use Image:play.gif, be sure to adjust the value for the animation delay time between consecutive simulation steps (the field labeled "Delay (ms):", see figure). Otherwise SUMO will run the simulation as fast as possible and you will probably see nothing happening at all. (Note that the the figure uses the style "real world" from the representation-dropdown-menu in the toolbar.)

The cars will drive from the beginning of edge1 to the end of edge2 and then leave the net (side remark: you can control the positions of departure and arrival by additional arguments to the flow, see Flow Definitions). The simulation ends when all vehicles have left the net.

Circular rerouting#

Now let us make the vehicles drive in circles around the track again and again. To this end we will create a rerouter

Create a rerouter in netedit (full implementation pending!)


Editing rerouters in netedit is not implemented completely currently. Alter the tutorial correspondingly, when this has been done! (See netedit#Rerouter)


In the future the editing of rerouters will be possible in netedit. Up to now rerouters have to be added manually (see below). Here is what can be done in netedit so far: Open your network circles.net and press a to enter the additionals edit-mode. From the dropdown menu "Additional element" on the left select rerouter and from "Edges" select edge1 (see figure). Then click somewhere in the editing window to create the rerouter (the rerouter icon is placed at the location where you click, but the location has no further meaning). Repeat the steps to create a rerouter for edge2.

Since in SUMO the additional elements are not considered as elements of the net, we have to specify them in a separate file (the "additionals-file"). Create and open a file circles.add.xml in the baseDir and add the following xml-code (see Rerouter/Assigning a new Destination for details):

    <rerouter id="rerouter_0" edges="edge1">
        <interval end="1e9">
           <destProbReroute id="edge2"/>
    <rerouter id="rerouter_1" edges="edge2">
        <interval end="1e9">
           <destProbReroute id="edge1"/>

Then we have to tell SUMO to include the rerouters into the simulation by adding a line to the config circles.sumocfg. Within the <input> tag add a child:

<additional-files value="circles.add.xml"/>

This will add two (destination-)rerouters to our network making the vehicles go around the circle until the given end time (i.e., until one hundred million seconds have passed). Effectively, each rerouter will update the destination for each vehicle entering its edge (specified by its edge-attribute) and set it to the edge given in the id-attribute of the destProbReroute-element. So as soon as a vehicle enters edge1 (its current destination), its destination will be updated to edge2 and vice-versa, when entering edge2 it will be rerouted towards edge1, thus following a circular route.


Here are some simple ideas to extend this toy example: twoloops.png

A net with two loops

  1. add more lanes in netedit and another vehicle flow with faster cars to observe SUMO's overtaking behavior.
  2. add a scooter flow and use the Sublane Model to observe SUMO's sublane model.
  3. add another loop (see figure) and trigger the next loop for each vehicle by a probabilistic choice of the destination (Rerouter/Assigning a new Destination), observe merging at the location where both loops are connected.
  4. Insert more vehicles, lower the simulation time-step length and try to observe stop-and-go waves, experiment with different car-following models, color the vehicles by speed.

If you create solutions for the exercises post them on this page!

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