[OSM-talk] Divided roads proposal

[Richard Bullock]

>>But to be completely honest, mapping out dual carriageways is really not
>>*that* time consuming. In JOSM you could just copy the way you have drawn
>>and drag the copied way a few metres to the side and reverse the 
>>direction.
>
>If that's the case, it sort of shoots down the "dual carriageway contains 
>more
>information than a single way" argument, doesn't it?
>
>Speaking for myself, what motivated my interest in this is that it is 
>tedious, and doesn't
>feel like the right thing to be doing. These minor roads don't seem like 
>they deserve too complete roads

No, it doesn't shoot down the argument. I just said it was an option if you 
couldn't be bothered to map it properly. And really, it doesn't take long 
anyway. And your proposed scheme for routing makes your scheme more 
complicated for the routers than mapping as two ways. In the existing 
scheme, if a shared node is not present between two ways, no routing is 
possible directly between the two. This is true regardless of what routing 
software you are using - it doesn't require extra tags or "fudges" to make 
it work. And think for a minute that there might be external data users who 
might not know to update their routing software for these extra tags. And 
not knowing about physically impossible turns is worse than not knowing 
about legal restrictions (turn restrictions).

I can't disagree more about "minor roads" not deserving to be mapped fully. 
We should map everything to the best of our abilities. And given the 
community we have, I'm sure someone will sooner or later - even if you find 
it 'tedious'. Some people actually enjoy mapping you know...

>Google Maps maps them as single roads.

Not around here.
http://tinyurl.com/yz8y8dh

The white coloured roads are just roads for a shopping centre. Scroll a bit 
further south, and you'll even see where G-Maps have split the road around a 
long-ish traffic island. A bit further south still, is a motorway junction 
where Google has mapped sliproads (and even marked on a sliproad bypassing 
the roundabout).

The Yahoo for the same location
http://uk.maps.yahoo.com/#mvt=m&lat=53.465566&lon=-2.354163&zoom=18

The principle we have used in the past is where it is not physically 
possible to cross between two carriageways without leaving the road surface 
then mark it as two separate ways. I've not seen a compelling argument 
against continuing this practice. The only argument I've seen from you is 
essentially, "it's boring - it takes far too long" - which I don't really 
agree with. Dual carriageways all over the world are mapped like this on OSM 
(and it seems Google, Yahoo and I'm sure others do as well).