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A traffic simulation game exploring how small changes to roads affect cyclists, transit users, pedestrians, and drivers.
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.github/workflows fix github actions after rust upgrade [rebuild] Mar 14, 2020
abstutil upgrade a few misc packages Mar 17, 2020
convert_osm converted the shell script into Rust. towards #27 Mar 26, 2020
data typography overhaul... [rebuild] Mar 26, 2020
docs typography overhaul... [rebuild] Mar 26, 2020
ezgui fix unicode characters that arent in roboto Mar 27, 2020
game highlight a certain person in a building [rebuild] Mar 27, 2020
geom more fixes for left-hand maps (#27): Mar 17, 2020
gtfs fixing the bug with grouping PSRC trips by unique person -- thanks to Mar 5, 2020
headless also group raw_maps in data/input Dec 3, 2019
importer moving popdat+precompute into the new unified importer Mar 26, 2020
kml converted the shell script into Rust. towards #27 Mar 26, 2020
map_editor typography overhaul... [rebuild] Mar 26, 2020
map_model adjust edit overlay color, and add an explicit reset button to edits Mar 21, 2020
popdat moving popdat+precompute into the new unified importer Mar 26, 2020
release moving game assets to data/system, to more easily bundle in wasm Feb 16, 2020
sim try a huge cutover to the new info panel organization. few implemented, Mar 27, 2020
.gitignore converted the shell script into Rust. towards #27 Mar 26, 2020
Cargo.toml moving popdat+precompute into the new unified importer Mar 26, 2020
LICENSE Initial import of A/B Street prototype. Mar 13, 2018 new release Mar 22, 2020 round of clippy. not fixing everything. Dec 12, 2019 adding a new hint for extra turn restrictions Aug 6, 2019 moving popdat+precompute into the new unified importer Mar 26, 2020 get halloween working with small lines. refactor a Line::maybe_new. Feb 1, 2019
rustfmt.toml tweaking rustfmt options; the long literal string vecs in tutorial lo… Jan 21, 2020

A/B Street

Ever been on a bus stuck in traffic, wondering why there are cars parked on the road instead of a bus lane? A/B Street is a game exploring how small changes to a city affect the movement of drivers, cyclists, transit users, and pedestrians.

Removing dedicated left-turn phases from a traffic signal:


Watching the Mercer backup start at 4am:


Documentation for developers


  • The map
    • A detailed rendering of Seattle from OpenStreetMap and King County GIS data, including sidewalks, on-street parking, bike lanes, bus-only lanes, turn lanes, buildings, and bus stops.
    • Intersections governed by stop signs and traffic signals, with default signal timings heuristically inferred. Hand-tuned geometry to reasonably model Seattle's strangest intersections.
    • You can adjust lane types, stop signs, and traffic signals, and reverse lanes.
  • The traffic
    • Individual cars, buses, bikes, and pedestrians move through the map.
    • Most trips are multi-modal -- for example, a pedestrian exits a building, walks a few blocks over to their parked car, drives somewhere, looks for parking, and walks to their final destination.
    • A realistic set of trips -- how many people go from building 1 to building 2 at some time using some form of transport -- based on PSRC's Soundcast model.
  • The gameplay
    • Start in sandbox mode, exploring the map, watching traffic patterns, following individual agents, looking for problems.
    • Jump to edit mode, where you can convert some on-street parking to bus lanes and adjust traffic signals to try to fix some problem.
    • Try your change in A/B test mode, running two traffic simulations side-by-side. Explore how individual agents finish their trips faster or slower, and compare aggregate results about different groups of traffic.
    • Attempt a predefined challenge with particular objectives, like speeding up certain bus routes or designing a full bike network.


In February 2020, user-testing and polishing before a wider announcement. After that:

  • Model more things: light rail, shared bike/walking paths, ridesharing, utility functions for different groups
  • Improve map and demand data quality
  • Continue polishing the UI and improving data visualization
  • More challenges and exploring radical new ideas (like Madrid superblocks)
  • Expand to other cities
  • Implement a web version

Project mission

If you fix some traffic problem while playing A/B Street, my ultimate goal is for your changes to become a real proposal for adjusting Seattle's infrastructure. A/B Street is of course a game, using a simplified approach to traffic modeling, so city governments still have to evaluate proposals using their existing methods. A/B Street is intended as a conversation starter and tool to communicate ideas with interactive visualizations.

Why not leave city planning to professionals? People are local experts on the small slice of the city they interact with daily -- the one left turn lane that always backs up or a certain set of poorly timed walk signals. Laura Adler writes:

"Only with simple, accessible simulation programs can citizens become active generators of their own urban visions, not just passive recipients of options laid out by government officials."

Existing urban planning software is either proprietary or hard to use. A/B Street strives to set the accessibility bar high, by being a fun, engaging game.



Help always needed! If you want to bring this to your city or if you're skilled in graphic or user experience, traffic simulation, data visualization, or civic/government outreach, please contact Dustin Carlino at or post at r/abstreet. I also welcome any contributions on Patreon.

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