I am trying to create an absolute center line layer from US interstate data that is multi-digitized (center line for each direction). I've looked at various options but they require a lot of processing involving voronoi polygons or adding points to lines and using a buffer or averaging those points. They work on very small data sets but anything larger slows down considerably to the point where it would be faster to do it by hand.
I'm currently trying to get v.centerline in GRASS to work but the documentation on it is very limited so I'm not sure if it will accomplish what I'm doing.
It seems that Esri has a tool that will do this. Is there an equivalent in QGis?