qgis - Merging close lines using v.clean

I downloaded some road network data derived from OSM by GeoFabrik, see the initial state: Near Székesfehérvár (Hungary), parallel lines are probably trunk or motorway roads.

I would like to simplify it like this (drawn in Paint):

I would like to use open source stuff for that (QGIS, GRASS), so I tried v.clean and v.simplify, v.generalize in some combination. Unfortunately, I cannot reach the desired result.

With v.clean 'snap' method, tolerance=50 I reached this:

But I don't need duplicated geometries, or identical zig-zag lines. Probably the v.generalize.network (Closeness, Betweeness threshold) would solve the problem, if it worked.

You can download the clipped geodata here: https://github.com/ewirth/gistemp

Answer

Buffering the road may be a solution to this problem.

• 
  

  create a dissolved buffer of the road using around 20 unit map distance.

  
  


• 
  

  import the layer into a postgis database and create the middle line using ST_ApproximateMedialAxis() function:

  
  

SELECT ST_ApproximateMedialAxis(geom) AS geom INTO road_centre_line FROM road_buffer;

• in order to access this function you have to enable the postgis_sfcgal extension


• with this you will get an output like this