Are entities in a many-to-many relation related individually?
As far as I could understand, there are 3 entities here.


Map
Road
Road Segment


And the relationships between them are:


Map M:N Road
Road 1:N Road Segment
Map 1:N Road Segment


A map could have multiple roads and a road could in multiple maps. A road could have multiple segments, in each map it is a part of. And a road segment would be related to one map and one road.


And to identify whether two segments are related to same road we can query the Road Segment entity to get which segments are related to same roadId.