Relations added to roads

I often see major highways created with many sections, sometimes with identical tags, sometimes differing, which is totally understandable.
But often there has been a relation also created for the entire road length, usually named the same as the Hwy Ref.
Over time, with people adding additional info (such as bridges & making dual carriageways), these relations become incomplete.

Where do these “Hwy number” relations get used, and how important is the rectification of the split/missing ones ?

I am guessing a good part of them were made by me. This is a habit I brought with me from the Danish community.

I honestly don’t know how many applications out there rely on it or what they use it for.

Personally I use it as an easy way to load and verify an entire route by simply loading the relation. I don’t know of a simple way to load routes based on the ref, especially when multiple refs share the same piece of road.

So I don’t really know how important they are, but I personally find them useful.

There is some discussion about it here:

These discussions are slightly interesting, but doesn’t provide much of an argument either. Just thought I’d post them anyway.

I don’t know what applications actually are using the relations for routing.

Public transport relations are in active use.

I suggest to keep existing relations intact while editing. JOSM will do most of it automatically for you. Be careful with the Web editors. They have a horrible reputation of breaking relations.

If interested in repair or check the relations have a look at the various QA tools like relation analyzer and such.