od2net

WARNING: This repo is not ready for general use. The API and input/output formats will keep changing. There are big limitations not yet documented.

TODO: Write intro

Create origin/destination requests
Calculate routes, and count how many trips cross each road segment
Filter for most popular segments that lack appropriate cycling infrastructure

Customizing

The purpose of this tool is to generate route networks quickly for areas up to national scale. The different stages of the pipeline are all modular and customizable, and to get meaningful results, we'll need to improve the defaults in all of them.

Generating requests

The pipeline needs a list of routing requests to run -- just a huge list of start/end coordinates. These should not be centroids of a large zone or anything like that.

Built-in options for "requests" currently include:

{ "Generate": { "pattern": "FromEveryOriginToOneDestination" } }
- One trip for every $AREA/origins.geojson to the first point in $AREA/destinations.geojson
{"Generate" : { "pattern": "FromEveryOriginToNearestDestination" } }
- One trip for every $AREA/origins.geojson to the nearest (as the crow flies) point in $AREA/destinations.geojson
{"Odjitter": { "path": "file.geojson" } }
- Use LineStrings from a GeoJSON file. You can use odjitter to generate a number of trips between zones, picking specific weighted points from each zone.
- Note this option is not recommended for performance. For an interesting amount of requests, the overhead of reading/writing this file full of requests and storing it in memory doesn't work.

Problems to solve include:

OSM is missing buildings in many places
Origins and destinations should be weighted, based on how many people live or work/shop/go to school/etc somewhere

Routing

The pipeline currently has two methods for calculating a route, specified by "routing":

The built-in "FastPaths" option, which currently makes a number of very bad assumptions:
- Every edge can be crossed either direction
- When `"cost": "Distance", edge cost is just distance -- equivalent to calculating the most direct route, ignoring LTS
  - "cost": "AvoidMainRoads" uses hardcoded multipliers for main roads
- No penalty for elevation gain
- No handling for turn restrictions, penalties for crossing intersections, etc

Scoring route likelihood

Even if a route is perfectly safe, it might be unlikely somebody would use it just based on the total distance or hilliness. The configurable "uptake model" assigns a probability between 0 and 1 to every route, and this value is summed for each edge.

The possible values for "uptake":

"identity" -- every route counts as 1, equivalent to just counting every trip
{ "CutoffMaxDistanceMeters": 16000 } -- trips over 16km are skipped entirely, otherwise they count as 1
"GovTargetPCT" and "GoDutchPCT" are uptake models from the PCT, using distance and gradient (currently hardcoded to 0)

Visualization

Open questions include:

How to visualize the counts for different road segments?
- Currently, direction is ignored
- Currently, we linearly interpolate line width based on the min/max count of any edge. Optionally can clamp the upper limit to handle outliers.
How to judge how suitable roads currently are for cycling
- Currently using BikeOttawa's Level of Traffic Stress code
Could we also visualize how easy a road is to modify? (Looking for excess width, parking/turn lanes, etc)

TODO

Some of the most important next steps:

Check the validity of using rstar on WGS84 coordinates. I think since the distances are so small, it's OK to pretend we're in Euclidean space.
Directly read in the graph from OSRM, so we don't have to reinvent the wheel for edge costs
Explore a UI for comparing counts from two different runs (so we can compare OSRM with our own cost function, for example)
Handle bidirectionality end-to-end -- track count in both directions, and produce a directed input graph

Longer-term:

Explore edge bundling to deal with dual carriageways and similar. Or maybe this is just a UI problem
Add an example of modifying the network to represent improvements
- aka, Ungap the Map v2
Make this entire thing easier to run -- generate configs using the web UI?
Validate output counts against current numbers (switching to a quiet/balanced profile first!)

stuartlynn / od2net