openstreetmap - Finding "terminal" cities on the map

I want to find villages/cities which are ends. That means: I need this villages which are linked to maximum one village on a distance of X km.

I'm just wondering how is this algorithm is called (I guess someone created something similar before).

Is there a tool for this? How is this concept called?

E.g.

 City ------------ Village 1 ------- Village 2 ------ Village 3 - - - [ Mountain]
                    \                 \                                \
                     Village 4         |                                Road
                     |                  \                            in mountains
                     Village 5----------Village6---------Village7 - - - - -  

As long the Road in mountains is longer than Xkm, Village 3 and Village 7 would be considered by me terminal, because they are linked to one village (V2, respectively V6).

Otherwise, I will want to build one with the open data we have.

---

What I've tried:

Downloading the OSM data for my country (Romania) and importing the villages and cities into the database. Using the geolocation functions from the database I'm able to find the villages which do not have more than X villages in the radius of R km.

However this is not a solution for my case because in my cases a village may be on the other side of the mountain, like in the example above, but there is no good way to it (or no way at all).