[OSM-talk] Divided roads proposal

Steve Bennett stevagewp at gmail.com
Sun Dec 6 13:48:01 GMT 2009


On Mon, Dec 7, 2009 at 12:30 AM, Lester Caine <lester at lsces.co.uk> wrote:

> I think my only problem with 'divided' is "At what point do you apply it?"
> The
> samples being shown are quite clearly - on the whole - dual carriageway
> structures.


(Just on terminology, I'm used to "dual carriageway" only being applied to
motorways, but Wikipedia says it technically applies to any road. We'll go
with that, then, ok.)

By "are clearly dual carriageway structures", I take it you're
distinguishing between roads which have a shortish traffic island of some
type, versus those which are divided for a long stretch. Is this important?

Example 10 clearly has a more complex structure than can be mapped
> by showing a 'divided' tag, since there is no access to the joining road
> from
> the other carriageway?
>

Have you read the proposal?

http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road

It covers *exactly* this case. In my proposal (ie, not Vovanium's, which
cohabits the page),  when there's a junction (like the road entering from
SW), by default that road can't cross the median - there is no gap. You can
see how this looks in my mocked up Halcyon image.


>
> Example 6 has some quite complex slip roads that really need isolated ways
> for
> the main carriageway. Trying to ADD tags to supplement a simple 'divided'
> tag to
> explain the slips on and off at the end is handled much easier with a
> simple
> dual carriage way?


Do slip ways need to be modelled at all? At the moment, they're not, as far
as I have seen. Essentially what is going on at that intersection is very
straight forward: divided road meets (temporarily) divided road, and all
turns are possible. Currently, I don't think many people would map the N/S
as divided (ie, two ways). With this proposal, you could do so, without
creating a mess.


> And many of the other examples need the same end cases. So at
> what level does a simple 'divided' tag actually work in practice? However
>

IMHO, the divided tag is well suited to all cases except 6, 7, and 9. Number
2 in particular is a perfect example. Worth tagging, not worth splitting the
road in two for.


> 'double white lines' on a single carriage way road IS a divider that needs
> tagging?
>
>
Yeah, I deliberated over whether or not to include that. What do you think -
same proposal, or separate? Double white lines really aren't a "divider",
they're a restriction on overtaking.

Steve
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