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.