I just spent a couple of days in Spain and mapped a couple of roads here (my first real additions to OSM) and was very excited when my first additions showed up on the maps :-).
The streets I mapped are all very small (most of the time two cars would have trouble passing each other) and are rarely used. They are mainly used to access properties along the roads, but could be used for through traffic by cyclists etc. if they prefer not to cycle along the main roads.
Some of the roads I recorded are paved. But on one of the roads the pavement is in a very bad state. How should I map that?
Yet another road which is not paved is in an extremely bad state as well. If one travels on it by car, one can often not drive any faster than walking speed in a normal compact car. It is a real consideration to go along way around this road to avoid having to drive that road and strain one’s shock absorbers ;-). If I just map it with surface=unpaved, than this does not really show.
I’ve had difficulty choosing whether to tag such roads as unclassified or as tracks: to a large degree the difference will be better understood by a local person. If the roads have significant traffic, for instance to a group of houses, or a considered to be a natural part of the local road network then I’d go for unclassified, otherwise use track.
I’d have a look for places in Spain which have been mapped by local mappers (or try asking on the Spanish list). Here’s an area (http://osm.org/go/b8opE6r) I know with some places I’ve driven. These have all been mapped by a local as highway=track. For instance the track which is aligned with the western boundary of Malpartida de Caceres is a decent quality unsurfaced road: dusty, but hard-packed. In this area most are used for access to farms, but use by non-locals in cars seems to be pretty much tolerated.
On the other hand this classified local road (http://www.openstreetmap.org/browse/way/50557319) was in appalling condition last year: it was instructive to see a police car coming in the opposite direction doing just as much weaving between the pot-holes as anyone else.
The one thing I would not do is use highway=unpaved. This tag has fallen out of use because a) the surface tag does the unpaved bit and b) you miss whether its a residential/unclassified/whatever type of road. Most apps using OSM data will not route on surface=unpaved either.
There is highway=road for roads where (for various reasons) the mapper is not confident of status: effectively this is a request for someone to check this road out.
Seriously, ask on talk-es. There are plenty of folk who are happy to answer in english.
Smoothness becomes hard science when the smoothness grade is not stable due to seasonal changes of the surface. Melting snow might cause heavy rasputitsa on unpaved roads. Riding a bicycle might be nearly impossible on such roads. The surface is almost like quick sand. What would be the best way to tag rasputitsa?
I checked what the locals did by looking at other roads in the vicinity that are similar using aerial imagery and noticed that the other similar unpaved roads are mapped as tracks. Interesting since it is not what I thought at first, but it seems appropriate to me now.