Traffic Generation¶

OpenCDA supports two different ways to generate the traffic flow: CARLA traffic manager and Sumo traffic simulation.

CARLA Traffic Manager¶

OpenCDA support researchers use the CARLA built-in traffic manager to control the traffic flow. All the test scripts that utilize CARLA traffic manager should have names ending with ‘carla’, e.g. single_2lanefree_carla.py, single_town06_carla.py.

To generate the CARLA traffic flow, users need to define the corresponding parameters in yaml file and call the APIs in opencda.scenario_testing.utils.sim_api.ScenarioManager:

Check the carla_traffic_manager in yaml rule section to see how to define parameters related to carla traffic in the yaml file.
Utilize ScenarioManager to generate CARLA traffic flow is easy. It just takes 3 lines of codes. scenario_manager.tick() will keep the traffic manager keep running during the simulation loop.

import opencda.scenario_testing.utils.sim_api as sim_api
# scenario_params are defined in the yaml file
scenario_manager = sim_api.ScenarioManager(scenario_params,
                                           opt.apply_ml,
                                           xodr_path=xodr_path,
                                           cav_world=cav_world)
# create background traffic in carla
traffic_manager, bg_veh_list = scenario_manager.create_traffic_carla()

while True:
    scenario_manager.tick()

Sumo Traffic Management (Co-Simulation)¶

OpenCDA provides the interface to enable users control the CAVs in CARLA and manage the traffic flow in Sumo . All the test scripts that utilize CARLA traffic manager should have names ending with ‘cosim’, e.g. single_2lanefree_cosim.py, single_town06_cosim.py.

To generate the Sumo traffic flow, three things are needed:

Define the Sumo server settings in yaml file. Check here to see more details.
Three files that defines Sumo road network and traffic route: a xxx.sumocfg file, a xxx.net.xml file, and a xxx.rou.xml file. xxx is the name of the testing map, e,g. Town06. This name should keep consistent acroos the three files.
- .sumocfg : used to give the Sumo server the path of the network and route xml file. Check .sumocfg file extension to see more explanations.
- .net.xml : defines the road graph. Check Sumo Road Networks to see more details. This xml file can be converted from your xodr file:
```
cd root/of/OpenCDA
python scripts/netconvert_carla.py your_map.xodr -o your_map.net.xml
```
- rou.xml : defines the traffic flow. As the example presents below, vType is used to define the vehicle types and flow defines the route. In this example, the server will generate continuous traffic flow in the first and second lanes of the road -63. Both lanes’ vehicles will try to reach road -62 via road -61 with a speed of 15 m/s. To know more details about the parameters’ meaning in route file, check Sumo Vehicle and Routes.
```
<routes>
<vType id="vType_0" minGap="2.00" speedFactor="normc(1.00,0.00)" vClass="passenger" carFollowModel="IDMM" tau="0.6"/>
<vType id="DEFAULT_VEHTYPE" minGap="2.50" tau="1.0"  color="255,255,255" Class="passenger" accel="0.5"/>
<flow id="flow_0" begin="0.00" departLane="1" departSpeed="15" departPos="-320" from="-63.0.00" to="-62.0.00" via="-60.0.00" end="4800.00" vehsPerHour="1000.00" type="DEFAULT_VEHTYPE"/>
<flow id="flow_1" begin="0.2" departLane="0" departSpeed="15" departPos="-320" from="-63.0.00" to="-62.0.00" via="-60.0.00" end="4800.00" vehsPerHour="1000.00" type="DEFAULT_VEHTYPE"/>

</routes>
```

Use CoScenarioManager to load sumo files and create sumo traffic flow. During initialization, CoscenarioManager will setup the Sumo server. During the tick() function, CoScenarioManager will keep spawning Sumo vechiles as traffic flow.

import opencda.scenario_testing.utils.cosim_api as sim_api

# there should be a Town06.sumocfg, a Town06.net.xml, and a Town06.rou.xml in
# Town06 folder
sumo_cfg = 'Town06'

# create co-simulation scenario manager
scenario_manager = \
    sim_api.CoScenarioManager(scenario_params,
                              opt.apply_ml,
                              town='Town06',
                              cav_world=cav_world,
                              sumo_file_parent_path=sumo_cfg)

while True:
    scenario_manager.tick()