[Tagging] usage of maxspeed:practical is described as recommended on wiki

[Richard Z.]

On Sat, Aug 23, 2014 at 10:33:16PM +0200, Martin Koppenhoefer wrote:
> 
> 
> > Il giorno 23/ago/2014, alle ore 21:08, Ilpo Järvinen <ilpo.jarvinen at helsinki.fi> ha scritto:
> > 
> > How much of such ways that would be a candidate for maxspeed:practical
> 
> 
> IMHO this is a highly subjective tag that depends heavily on your driving ability and the vehicle and driving comfort you expect. E.g. a moderately modern battle tank can drive 70-90km/h on an open field with no road at all ;-)

as I wrote on the talk page I am fully in support to update the
proposal to include modern tanks and other relevant vehicle types.

> As we are generally rejecting subjective tagging like suitability and the like, this practical speed tag does not fit well in our system

It just fills a gap. Many other tags such as track type and even 
highway type (primary/secondary...) are highly subjective and used
very differently from country to country. There is no reason to think
track types are any more objective than maxspeed:practical.

Just tagged a road in the Seychelles as tertiary.. I remember it 
is a slightly difficult single lane partially paved road with 
a steep incline in some places. Even if I would remember every 
single detail of the road and use all existing tags - what can 
you deduce from that? What can routing software deduce from it?
If I add maxspeed:practical=25 everyone from anywhere in the world 
has a first idea what to expect. Even if people would argue that
it should be 15 or 30 instead of 25, all other tags taken together 
are not anywhere close to help you predict a similar value.

Richard