OpenStreetMap
There is an open dataset of turn restrictions in Toronto which gives a rare opportunity to completely map every restriction in the city.
Inspecting the dataset in QGIS
The dataset consists of the topology of road centerline of every junction in the city, and at every junction, each possible turn direction is an individual line with a property that indicates the type of restriction on it.
Most of the restrictions are u-turns and no turns into one ways. The only restrictions which look valuable to add into OSM seem to be the no turns (By law) which number about 520.
All turns at a junction with their restriction status
Improving OSM
It seemed like an interesting exercise to compare this with the restrictions already mapped on OSM and check if it can be used for validation or add missing ones. To do this, try this simple data tool to browse the Toronto restriction dataset and verify it against the map.
Turn restrictions in Toronto (Red: no left, Orange: no right, Green: no straight) on the data-mapper tool
Clicking on the map allows you to open the location in JOSM, and also set a review marker. You could either review it as:
- Valid: Restriction is valid and has been added to OSM
- Redundant: Restriction is correct, but is not required to be added onto OSM (eg, no turn into a oneway)
- Invalid: Incorrect restriction
The existing OSM restrictions show up as purple lines once you zoom in. Interestingly, I could notice plenty of restrictions on the map that is not present in the Toronto dataset, so looks like the map may actually be more updated in many areas than the data the city has.
Feel free to explore and share your observations. Toronto could well become the first city on OSM with comprehensive turn restriction data that is verified against an official data source.
Discussion
Comment from joost schouppe on 6 July 2016 at 07:42
This is extremely interesting!
We have a lot of open geodata these days, and a tool like this might make it so much easier to conflate those with OSM. I’ve been experimenting with this recently, for example taking an open data feed and a live Overpass query to compare mapping quality and completeness (case: dog parks).
The list of “invalid” items is something which might be quite valuable to the official data sources. In Flanders (the northern half if Belgium), we now have very extensive road and path open data. It is more complete than OSM, but it is also often outdated. So a matching is going to be a lot of work. Do you think the data-mapper could be adapted to something as big as this? See this thread for info and a comparison map.
Comment from PlaneMad on 6 July 2016 at 09:29
joost, the purpose of the tool was exactly to help such projects where we need to compare and merge data into OSM. I think i’ll need to do a bit more work till its easily customizable, tracking updates here: https://github.com/osmlab/data-mapper
Comment from joost schouppe on 6 July 2016 at 11:31
Interesting stuff anyway. A toolchain is getting born :) I was just made aware of this project, that creates a simple report about the comparison between OSM and reference road data. We couldn’t get it to work, though.
Comment from PlaneMad on 2 August 2017 at 09:05
Great blog by Anita Graser on using WGIS to do QA of this data: https://anitagraser.com/2016/07/23/osm-turn-restriction-qa-with-qgis/