Distributed deep reinforcement learning traffic signal control framework for SUMO traffic simulation.

YouTube Video Demo

This code is an improvement and extension of published research along with being part of a PhD thesis. Please cite the following reference if you use this code in your own research:

@article{doi:10.1080/15472450.2018.1491003,
author = {Wade Genders and Saiedeh Razavi},
title = {Asynchronous n-step Q-learning adaptive traffic signal control},
journal = {Journal of Intelligent Transportation Systems},
volume = {0},
number = {0},
pages = {1-13},
year  = {2019},
publisher = {Taylor & Francis},
doi = {10.1080/15472450.2018.1491003},
URL = {https://doi.org/10.1080/15472450.2018.1491003},
eprint = {https://doi.org/10.1080/15472450.2018.1491003}
}

• Python 3.6
• Ubuntu 18
• Sumo 1.1.0
• Tensorflow 1.12 (optimized builds here)
• SciPy
• Keras 2.2.4

python run.py -nogui -save -mode train

To learn more about all input arguments, run python run.py --help.

After training has completed, execute:

python graph_actors.py

to create a visualization of actors with different action explortation rates, similar to:

When training, optimal execution requires balancing the number of parallel actors -actor and learners -learner. A simulation with a single intersection can be left at the default settings (i.e., 1 learner and the rest actors). As the number of signalised intersections in the network increases, more learners will be required. Agents are distributed to learners in an approximately equal fashion; each learner is responsible for performing batch updates for their assigned subset of agents (e.g., a network with 13 signalised intersections and 3 learners would allocate 4, 4 and 5 intersections to the learners). Each actor is assigned an epsilon greedy exploration policy from equally spaced intervals between a random policy and a defined greedy policy -eps 0.05 (e.g., with 4 actors and -eps 0.05, the actors implement one of [1.0, 0.68, 0.37, 0.05] epsilon greedy policies).

To watch learned agents, execute:

python run.py -load -mode test -actor 1 -learner 1

This framework takes a SUMO network simulation and develops deep reinforcement learning agents for each signalised intersection to act as optimal signal controllers. A distributed actor/learner architecture implemented with Python multiprocessing enables hardware scalability. This research implements n-step Q-learning, an off-policy, value-based form of reinforcement learning.

Two simple SUMO simulations are included, the first (-netfp networks/single.net.xml -sumocfg networks/single.sumocfg) with a single intersection:

and the second (default) with two intersections:

Vehicle generation is implemented in Vehicle.py class. Vehicles are generated uniform randomly over origin edges with their departure times into the network modelled as a Poisson process. SUMO subscriptions are used to optimize performance accessing vehicle data. Yellow and red phases are inserted between conflicting green phases, their duration controlled by -yellow 4 -red 4.

The n-step Q-learning algorithm is used to train agents to implement acyclic, adaptive traffic signal control. An agent's policy selects the next green phase for a fixed duration. Green phases can be selected in an acyclic manner (i.e., no cycle). The fixed duration (i.e., action repeat) of the green phase is controlled with -arepeat 15. Smaller action repeats enable more frequent control but are likely more difficult to learn. The agent's state is a function of the density of all incoming intersection lanes. The reward is the negative cumulative delay of all vehicles on incoming lanes. The default deep neural network is a 2 hidden layer fully-connected architecture to model the action-value function, implemented in NeuralNetwork.py.

In -mode train the actors first execute until all experience replays are filled -replay 10000. Then actors continue to generate trajectories until learners perform sufficient batch updates -updates 10000. In -mode test the actors execute 1 simulation.

Consult the SUMO Wiki and API docs for additional help.

My PhD thesis on this topic

Some of my other reinforcement learning traffic signal control research