LTS-OSM - Calculating Level of Traffic Stress using Open Street Map Data

This code calculates cycling Level of Traffic Stress for all road and path segments in a region using data from Open Street Map.

View the data on a map

You can view the LTS map for GTA at https://bikespace.ca/lts-map

Background

This code is adapted from Bike Ottawa's LTS code, modified to include Level of Traffic Stress for intersections. This is code is forked and adapted from Madeliene Bonsma-Fisher's LTS_OSM implementation, it has been adapted to be have a more generic and adaptable use, majority if not all of the logic remains intact from her implementation.

Usage

1. Setup a python virtual environment

	python3 -m venv venv

	#active the virtualenv
	source venv/bin/activate

	#Install the dependencies
	pip install -r requirements.txt

2. Create a query JSON file listing the areas you want to study.
   • Go to openstreetmap.org, search for the region (e.g. "Victoria"), click the matching relation, and scroll to find the wikidata tag (e.g. Q2132).
   • Create a JSON file (see query/gta.json for an example) with an areas array:

   {
       "areas": [
           { "name": "victoria", "wikidata": "Q2132" }
       ]
   }

3. Run the script to download OSM data and calculate LTS:

	# Download from Overpass and calculate LTS for all areas in the query file
	python lts_osm/lts_osm.py --query-json-file query/gta.json

	# Outputs are saved to a timestamped run directory: output/runs/<timestamp>/

	# Re-run LTS calculation using already-downloaded XML files (skips Overpass download)
	python lts_osm/lts_osm.py --downloaded-xml-json-map output/runs/<timestamp>/areas_xml_file_path.json

	# For help:
	python lts_osm/lts_osm.py --help
	usage: lts_osm.py [-h] (--query-json-file QUERY_JSON_FILE | --osm-file OSM_FILE | --downloaded-xml-json-map DOWNLOADED_XML_JSON_MAP)

	Calculates the Level of Traffic Stress from Open Street Map data.

	options:
	-h, --help            show this help message and exit
	--query-json-file QUERY_JSON_FILE
							Path to query json file indicating which area(s) to download from OSM
	--osm-file OSM_FILE   Path to a single downloaded OSM XML file
	--downloaded-xml-json-map DOWNLOADED_XML_JSON_MAP
							Path to a json file mapping areas to their downloaded xml paths

4. Plot the results with lts_osm/lts_plot.py

	# Supply the lts csv files generated by lts_osm.py and the name of the city
	python lts_osm/lts_plot.py --lts-csv-file output/runs/<timestamp>/lts_csv/all_lts_toronto.csv --gdf-nodes-file output/runs/<timestamp>/lts_csv/gdf_nodes_toronto.csv --city "Toronto"

Converting geojson output to PMtiles

To render the LTS dataset on bikespace.ca we convert the outputted gejson into PMTiles. PMTiles is a single-archive format for tile data. It is a 2-step process, first the geojson has to be converted into MapboxTile format mbtiles and then converted to pmtiles. To convert the resulting geojson file you'll need to install 2 tools:

• tippecanoe
• pmtiles

# Converting to mbtiles
tippecanoe -l lts_toronto_filtered_1_4 -n "Level of Traffic Stress" --no-feature-limit --extend-zooms-if-still-dropping --coalesce-densest-as-needed --maximum-tile-bytes=2000000 -P -zg -D12 -o [output_file.mbtiles] [input_file.geojson]

# Converting to pmtiles
pmtiles convert [input_file.mbtiles] [output_file.pmtiles]