How to correctly map ferries

I have a small problem on mapping some ferries routes across Danube in my home town Galati, and also in the neighbour town Braila (both towns are in Romania).

In Galati I used to map the ferry route just using route=ferry, but no highway tag (I changed that on 25th August so have a look on Mapnik as Osmareder tiles are already updated) http://www.openstreetmap.org/?lat=45.41336&lon=28.03507&zoom=15&layers=B00FTF , but in Braila I used also highway=primary tag http://www.openstreetmap.org/?lat=45.28798&lon=27.99848&zoom=16&layers=B00FTF. When trying to use the demo routing web applicatioan here: http://tile.openstreetmap.nl/~lambertus/routing-world/ it seems like the we can’t use the ferry route in Galati, only the one in Braila, and I believe this happens because the Braila ferry route is also tagged as highway=primary.

Look at these routes: Braila - Tulcea (you are routed through Braila ferry, correct) http://tile.openstreetmap.nl/~lambertus/routing-world/?flat=45.271133&flon=27.97329&tlat=45.177925&tlon=28.801896&v=motorcar&fast=1
Galati - Tulcea (you are also routed through Braila ferry, incorrect, we should use Galati ferry) http://tile.openstreetmap.nl/~lambertus/routing-world/?flat=45.433732&flon=28.055149&tlat=45.177925&tlon=28.801896&v=motorcar&fast=1

My question is this: what is the correct way of tagging ferry routes in this case (crossing a river, not crossing a sea)? Should we also use highway tag?

I hope I provided enough information, if not please let me know.

You should not use the highway tag.
The problem with routing is a bug in the routing software.

Well, it might be my fault then, because if I set the options to find the shortest route, the result will be the desired one (through Galati ferry). I just removed the highway tag from the both ferries and when the planet file for the route application will be updated I will check the new results.

You will have to file a bug report to the people doing the Gosmore(?) routing engine.