Importing a new city into A/B Street

If you get stuck, please email or file a Github issue. I promise quick turnaround time. All you need to do is send the boundary of the area you want, drawn with

The easy method

This only works in the downloaded version, not on web.

  1. Click the map name in sandbox mode to change your location.
  2. Click "import a new city"
  3. Follow the instructions. That's it!

This may take a few minutes, depending on download speed. Be sure to use the polygon tool to draw an area, not the polyline tool.

If the city has already been imported

A/B Street includes many cities already. Once you're running the game (natively or on the web), click on the Sandbox option, then check the top for a button to change the map:

You can browse through a list of cities per country, or use a text search:

You may need to download data for that city:

You should be able to open the map. In this case above, the map data was saved as data/system/gb/exeter_red_cow_village/maps/center.bin.

How to pick boundaries

How do you decide what part of a city to import? It can be tempting to use pre-existing administrative boundaries. There are a few problems:

  1. Official boundaries might exclude something relevant to transportation in the area. For example, London boroughs don't cover the River Thames or its bridges! Or if you're studying low-traffic neighborhoods, an area near the border of two boroughs might not include enough surrounding context.

  1. File size is hard to tune. You have to play around with this to make the resulting area large enough to be useful, but the map file small enough to comfortably load. About 50MB uncompressed (usually 20MB gzipped) is a good target.

  2. You might have to adjust the boundary to exclude the coastline and ocean, due to a bug.

You can create multiple districts covering a city. The districts can partially overlap, and you don't have to cover everything. It's totally dependent on what you want to study. The current Seattle boundaries are just based on different projects we've worked on:

You can also just make best geographic guesses like in Paris:

The more maps configured to always be imported, the slower my development workflow gets when working on map importer code. So I'd also request you don't go overboard and ask for lots of areas, unless you're going to actively work on some advocacy or research across multiple A/B Street releases. You can always import an area yourself in the UI.

Advanced: Using the command-line

The process above using the UI just calls a tool to do all of the work. If you want, you can just call that tool from the command line. First save a GeoJSON file with your boundary. Then...

Using a .zip release: ./cli one-step-import --geojson-path=boundary.geojson --map-name=prague

Building from source: cargo run --release --bin cli -- one-step-import --geojson-path=boundary.geojson --map-name=prague

The new map is located in the country with code "zz" (this isn't a real country), in the "oneshot" city. This is stored in data/system/zz/oneshot/maps.

Advanced: Adding the city to A/B street permanently

The easiest method is to just ask Dustin to do this. The full process:

  1. Make sure you can run -- see the instructions. You'll need Rust, osmconvert, gdal, etc.

  2. Create a new directory: mkdir importer/config/xy/your_city, where xy is a lowercase two letter country code from

  3. Use or to draw a boundary around the region you want to simulate and save the geojson locally.

  4. Use cargo run --release --bin cli -- geojson-to-osmosis boundary.geojson to convert that geojson to the Osmosis format required by osmconvert. This tool writes one file per feature in the input, so you'd then mv boundary0.poly importer/config/xy/your_city/region_name.poly, repeating if you drew multiple polygons.

  5. Edit importer/src/ if needed. If you're the first to import a new country, you may need to configure left-handed drivng, for example.

  6. Run the import: ./ --city=xy/your_city --raw --map

  7. Update .gitignore, following tel_aviv as an example. Keep sorted!

  8. Fill out nice_map_name in map_gui/src/tools/

Send a PR with your changes! I'll generate everything and make it work with updater, so most people don't have to build everything from scratch.

Also, you can divide the city into multiple regions, repeating step 4 and declaring more polygon boundaries. The boundaries may overlap each other, and they don't have to cover all of the space. Picking good boundaries may take trial-and-error; the goal is to keep the resulting map file size small, so that it loads quickly, while capturing all of the area needed to simulate something interesting. This is easiest when you have some local knowledge of the area, and at least a vague goal in mind for what you want to study.

Advanced: Importing a .osm file directly

This section assumes you're comfortable working on a command line. If you have a .osm XML file, you can import it directly by running cargo run --release --bin cli -- oneshot-import /path/to/extract.osm. If you're running from a .zip release and not building from source, replace the first part with ./cli oneshot-import.

Assuming this succeeds, it'll create a file in the data/system/zz/oneshot/maps/ directory. In the UI, you can open the "zz" country to find it.

If you save a .osm file from JOSM, you might get an error importing related to convert_osm/src/ If so, delete the <bounds> element from the top of the .osm file and try again.

If you follow this process, the resulting map won't have any border intersections, which will break parts of the simulation:


You can fix this by creating the Osmosis .poly file and passing --clip-path=/path/to/clip.poly to the import command.

One use case for following this section is to temporarily work around broken intersection geometry. The process is:

  1. Edit the problematic area in JOSM, recreating a complicated intersection in a simpler way.
  2. Save the .osm file locally
  3. Run the importer
  4. Try in A/B Street

You probably don't want to upload the changeset to OSM, unless it's actually mis-tagged. Usually the problem is how A/B Street tries to interpret what's in OSM. Ideally we could also follow this process using the ID editor, but it can't currently manage changeset files fully.

Next steps

OpenStreetMap isn't the only data source we need. If you look at the import pipeline for Seattle, you'll see many more sources for parking, GTFS bus schedules, person/trip demand data for scenarios, etc. Most of these aren't standard between cities. If you want to make your city more realistic, we'll have to import more data. Get in touch.

You may notice issues with OSM data while using A/B Street. Some of these are bugs in A/B Street itself, but others are incorrectly tagged lanes. Some resources for fixing OSM: