[OSM-talk] Divided/Non-Divided Intersection

[Nathan Edgars II]

Maarten Deen wrote:
>John Smith wrote:
>> On 11 July 2010 06:43, Chris Dombroski <cdombroski+osm at icanttype.org> wrote:
>>> I ask because I think this is the cause of stupid GPS directions at times
>>> "make a left, followed by a slight right"
>>
>> Isn't that a problem with the routing software, not the data?
>
>Not IMHO.
>
>If you have a layout like this (use a fixed-width font):
>
>      | |
>A----+-+
>      | +----B
>C----+-+
>      | |
>
>And you want to go from B to A, why would routing software say "go straight on"
>and not "go right, then go left"?
>
>And option is to map it like this:
>      | |
>A----+ |
>      |\|
>      | +----B
>      |/|
>C----+ |
>      | |

I use either this or a slight modification where ways A and C meet on
the left side and B continues across the right side. Usually I decide
based on whether A/C or B is a more major road, and thus what
classification the pieces in the middle should be.

In some US counties, the imported TIGER data treats an intersection of
divided highways as a single node:
http://www.openstreetmap.org/?lat=39.785241&lon=-75.546328&zoom=18&layers=B000FTF
This is IMO a horrible solution, especially when channelied left turns
are added between the main lanes. I changed a nearby stretch of US 13
to keep the main lanes straight, and it looks much better:
http://www.openstreetmap.org/?lat=39.70937&lon=-75.56229&zoom=17&layers=B000FTF