OpenStreetMap
A turn-restriction defines restricted or mandatory turns at a junction and are one of the most important features to map for accurate driving directions. Thought I would quickly make a comparison of how different map data editors visually represent this feature for mappers. Pick the best:
JOSM
Discussion
Comment from ikonor on 16 August 2017 at 20:42
There is also still the Map of Turn Restrictions by Zartbitter, it just moved to a new location (formerly at map.comlu.com). I updated the link at Relation:restriction > Tools.