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Traffic Modelling

A simple computer model for simulating traffic congestion.


  1. Install dependencies: npm install
  2. Generate configuration files: npm run configure
  3. Run simulation: npm run simulate


For an overview of the computer model and how it can be used, please see this article investigating whether lane changing in traffic is a zero-sum game.

Configuring the model

npm run configure generates two configuration files:

1. Common Configuration: config/common.json

Copied from the sample file: config/common.sample.json. Contains the following fields:

  1. arrivalProbability: Likelihood a car arrives on the next tick
  2. durationInTicks: How long each simulation runs for
  3. numberOfIterations: The number of times (iterations) each configured simulation is run. The result takes an average of all iterations
  4. simulationDefaults: The values of the Independent Variables used in all simulations, unless they are overridden in the simulation configuration
    1. laneChangeDelayTicks: The time added to the Total Time in Lane upon a lane change
    2. lanePlacement: How each Car is assigned to a Lane (levelled or random)
    3. minTicksInLane: The minimum time in Lane until Car considers switching Lanes
    4. minTickSpeedupPercent: The minimum time saved by switching Lanes for Car to consider switching Lanes
    5. numberOfLanes: The number of lanes (minimum 2)
    6. timeOnRoadFunction: The function t = f(n) used to calculate total time on road t. Based on n, the number of Cars in lane.
  5. output: Configuration for how simulation output is written
    1. format: File format (markdown or csv).
    2. path: File path (filename will be results).
    3. columns: Columns to include in results. Array of tuples. First entry is the variable name, the second is the column header used. Examples:
      • [ "minTicksInLane", "Min Time in Lane" ]
      • [ "overallThroughput", "Aggregate Throughput (cars / 100 ticks)" ]

2. Simulation-specific Configuration: config/simulations.json

Contains configurations for every simulation, where one or more Independent Variables can be overridden. This file is auto-generated by prompting the user, varying one Independent Variable at a time. Additional simulations can be added by editing this file directly (prior to running npm run simulate).

Running the simulation

npm run simulate runs the simulation and outputs debug data to the console. It also generates the results and writes them to the path and format as specified in the common configuration.

Traffic Performance Metrics

The following can be included in the results file by adding them to the common configuration (under output.columns):

  • simulationTime: Elapsed time of simulation
  • carsEntered: Total number of cars entered over the course of the simulation
  • carsRemaining: Cars remaining on the road at the end of the simulation
  • averageTimeOnRoad: Average time spent on the road by all cars
  • carsOnRoadAggregateTime: Total of all times spent by all cars on the road
  • totalLaneChanges: Total number of lane changes that occurred
  • overallThroughput: Measures traffic performance.
    • Aggregate Throughput (cars / 100 ticks) = Total Cars Exited / Aggregate Time * 100
  • averageThroughput: Same as above, except that it is calculated per tick, then averaged


  • Run tests while you code: npm run specs -- --watch
  • Run ESLint and all tests: npm test
    • NOTE: also runs in Travis CI
  • Run ESLint on its own: npm run lint
    • NOTE: not recommended, instead configure your IDE to use the project's ESLint configuration


A simple computer model for simulating traffic congestion.




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