[OSM-talk] Separate lane tagging

[Martin Koppenhoefer]

Am 5. März 2012 12:08 schrieb LM_1 <flukas.robot+osm at gmail.com>:
> Currently the recommendation about separate mapping of directions
> seems to be the existence of a physical divider (wall, grass...).
>  There is no problem if the divider is continuous and only has
> 'holes' in it to allow turning or lane changing during construction
> works.


when there are "holes" you will obviously have to split the divider
and keep the holes free.


> If the divider is only a small object like tram platform, it does not
> seem right to divide the way and connect it afterwards.


why not? IMHO you should so exactly this. There are also similar
situations like subway entrances and pedestrian crossing islands where
the carriageway is split.


>  If this is mapped according to the recommendation the street would
> be between two rails (trams cannot change rails), which is not true.
>  If each of the one way general traffic roads is mapped separately,
> it would seem that you cannot turn (you are not allowed to, but it is
> physically possible).


This whole "physically possible" field merits some further
considerations and discussions IMHO. First of all: physically possible
for whom? An old lady with a stick? A battle tank? A generic young
male acting as pedestrian? Possible with a vehicle with 2 axes 4
metres long and 1.8 wide or one 18 metres long and 2.3 metres wide?
Would a cyclist dismantle and lift his bike over a small fence to
avoid 3 km of detour? Would you risk damaging the tyres of your car
(could still be "physically possible") or do you prefer not to? This
all depends on a lot of different factors.


For instance some time ago some mappers started to use
highway=footway, footway=sidewalk to map sidewalks with dedicated
osm-ways. This will in many cases actually lead to worse routing
results, as a destination just on the other side of the road will make
your router suggest to go via the next crossing (however far that
might be), instead of telling you that you have already arrived.


cheers,
Martin