[OSM-talk] Should Bridges be independent of their ways?

[Martin Koppenhoefer]

2009/9/22 Anthony <osm at inbox.org>:
> It is possible to represent different surfaces and different maxspeeds
> without using more than one way.  "maxspeed:lane=130;110";
> "surface:lane=asphalt;concrete".  That's not necessarily the best solution,

indeed, it won't be understood by none of the apps that are using our
data and it doesn't say, which lane has which value...

> Different turn-restrictions is already possible.  If you have a three lane
> way with two lanes going straight and one turning right, you join three ways
> at one node: one with three lanes, one with two lanes, one with one lane.
> If you have a three lane road with two lanes going straight and one lane
> going straight or turning right, ditto, except the way going straight has
> three lanes instead of two.  Which lane is which is determined by the
> geometry of the ways as they come out of the node.

but that's exactly what I propose (map lanes explicitly) and it's
against the separate-ways-only-when-physically-divided-paradigm
(because an ambulance could change from one way to another)...

>> but I also see the pros:
>> - is easier to understand and more intuitive to edit: better
>> maintenance: you see what is there
>
> That's an editor consideration.  You can make it *look* like you're editing
> three separate ways when you're really editing one way with three lanes.

I knew someone would raise this argument, but please explain how the
editor will know where the lanes exactly go.

>>
>> - is more precise in terms of positional accuracy
>
> I'm assuming the lanes are parallel.  If not, then yes, you need to use
> multiple ways.

they will never be parallel for the entire lenght, at least there will
be a start and an end, but often they will also turn at junctions...
>>
>> - can better represent stuff like ramps for motorways (parallel ways
>> that currently are mapped like intersections), cyclelanes, ...
>
> Why are they being mapped like intersections?  They shouldn't be.  You mean
> a gradual merge is being mapped at a right angle?  That's wrong, and there's
> no good reason for it (other than didn't have the time to get it right,
> anyway).

I meant the lanes for acceleration and breaking (when going on or from
a highway). Usually there will be ~100mtres for this where you can
change at any time, but in OSM you have to decide on one merging
point.

cheers,
Martin