[Tagging] lanes tag dispute

Anthony osm at inbox.org
Sun Sep 18 18:34:54 BST 2011

On Sun, Sep 18, 2011 at 1:21 PM, Nathan Edgars II <neroute2 at gmail.com> wrote:
> On 9/18/2011 1:18 PM, Anthony wrote:
>> http://www.pocketgpsworld.com/reviews/tomtom-v8/v8_lane_assist_northwest2_speed_alert.jpg
>> Do you think Garmin is mapping every lane as a separate way here?  I
>> don't think they are, or that they should.  I think if I were going to
>> do it, I'd map this as one way up to the theoretical gore point, and
>> then as two ways after the theoretical gore point.  I wouldn't use
>> five ways.
> It's simple on a motorway. But, for a simple example on a surface road, how
> do you know where the straight lanes go if there are 3 lanes after an
> intersection but 2 before?

Depends on what data you have.  If you have lane width information,
then it's easy to figure this out.  If you don't, then you can't
figure this out.  If all lanes are parallel, you certainly don't need
a way for every lane, though.

But why is this important in the first place?

> And actually, even on a motorway, what if it's 4 lanes to a split of 2 and
> 3? The assumption is that the second lane from the left can be used to exit,
> but it's possible that only the leftmost lane is available, and a second
> lane begins on the ramp right at the gore. Or perhaps there's a short
> segment of 5 lanes before the split - how do you know which side the new
> lane forms on?

This can be determined by the geometry of the ways, which are mapped
at the center.

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