# [Tagging] lanes tag dispute

Nathan Edgars II neroute2 at gmail.com
Sun Sep 18 18:52:52 BST 2011

```On 9/18/2011 1:47 PM, Anthony wrote:
> On Sun, Sep 18, 2011 at 1:38 PM, Nathan Edgars II<neroute2 at gmail.com>  wrote:
>>> This can be determined by the geometry of the ways, which are mapped
>>> at the center.
>>
>> No they're not.
>
> On Sun, Sep 18, 2011 at 1:39 PM, Nathan Edgars II<neroute2 at gmail.com>  wrote:
>> On 9/18/2011 1:38 PM, Anthony wrote:
>>> Nevermind.  Yes you can.  If the center of the 3 lane road is to the
>>> left of the center of the 2 lane road, then the lane was added on the
>>> left.  If the center of the 3 lane road is to the right of the center
>>> of the 2 lane road, then the lane was added on the right.
>>
>> Ways are not mapped this way.
>
> Ways aren't mapped at the center?  Where are they mapped?

Somewhere between the two edge lines. Always using the exact center
would require zigzagging whenever lanes are created or destroyed.
>
>> And even if they were, this would only work if there's a median.
>
> What's a median got to do with it?

When there's no median, the center depends on both directions.
>
> On Sun, Sep 18, 2011 at 1:40 PM, Nathan Edgars II<neroute2 at gmail.com>  wrote:
>> Not to mention that the line between the lanes doesn't always go straight
>> through the intersection.
>
> Why does that matter?

Because if the pre-intersection right lane is directly behind the
post-intersection center lane, but an angled dashed line forces you into
the post-intersection right lane, this cannot be determined without
mapping this somehow.

```