# [Tagging] Lane geometry in OSM

Jmapb jmapb at gmx.com
Fri Aug 3 21:35:21 UTC 2018

```On 8/3/2018 5:31 PM, Tom Hardy wrote:

> On Friday, 3 August 2018 15:39:09 CDT Lionel Giard wrote:
>
>> You can tag it with :
>> lanes=3
>> lanes:forward=1
>> lanes:backward=2
>> turn:lanes:backward=left|through
>>
>> and split the way where the two arrows are located, and inverse the tagging
>> on the other segment (put the lanes:forward=2; lanes:backward=1;
>> turn:lanes:forward=left|through).
>> As i suppose you should not drive further than the arrow in either
>> direction. So you have "two turn lanes" facing each other (that's more or
>> less what it looks).
> Won't do; at least not in the general case.  https://binged.it/2AGqqTa should
> give a Microsoft street view that you can march along and examine; see how
> long it is, the periodic repetition of the double arrows, etc.  It's from
> another location where I remembered a lengthy center lane.
>
> The lane is used for left turns in both directions, and also to collect cars
> making left turns onto the street, as well as for emergency vehicles dealing
> with heavy traffic.  And yes, I find them to be a bit dangerous, for the case
> where cars heading in opposite rapidly and simultaneously enter the center
> lane.
>

(Sorry, did a private reply...) The accepted answer posted here:

https://help.openstreetmap.org/questions/64617/how-to-map-center-turn-lanes

is simply:

lanes = 3
lanes:forward=1
lanes:backward=1
lanes:both_ways=1
turn:lanes:both_ways=left (or right for drive-on-left regions)

Seems like it would work. It doesn't cover the possibility of emergency traffic in the center, of course, but emergency vehicles don't really follow the rules anyway. J

```