[Talk-us] I 85 Express Lane (Atlanta, Georgia)

[Tod Fitch]

> On Sep 24, 2017, at 5:22 PM, Minh Nguyen <minh at nguyen.cincinnati.oh.us> wrote:
> 
> On 22/09/2017 09:46, Jack Burke wrote:
>> My questions are:
>> * Should this lane be drawn as a separate way?  Legally, you cannot enter or exit the lane except at the designated sections, so drawing it separately makes things simpler for routers.  If it's drawn separately, a pair of motorway_link roads would need to be added at several places (the dashed-stripe sections).  The Lanes wiki page[4] seems to say that it should be drawn separately:  "If one or more lanes of the road are restricted to high-occupancy vehicles (typically vehicles with 2+ occupants, although this varies by jurisdiction). Most useful if entrance/egress is permitted at any point along the route; if entering or exiting the HOV lane(s) is only permitted at certain locations, modeling the HOV lane(s) as separate ways is preferable."  (Even though that says HOV, the same reasoning appears relevant for toll.)  Does everyone concur with this construction?
> 
> I might be inclined to map the lane as a separate way, but only because I don't know of any routers that currently recognize the change:lanes tag. [1] Either way, it makes sense to treat HOV and toll lanes similarly.
> 
> [1] https://wiki.openstreetmap.org/wiki/Key:change
> 

I strongly recommend mapping them as one way with the hov:lanes=* and change:lanes=* showing the restrictions and where you can transition between the lanes. That is the best tagging I know of to accurately reflect the actual configuration.

The reason I feel strongly about it is that many miles of HOV lanes in my are were mapped as separate lanes (done before I moved to the area). And now CalTrans is repainting those to allow entry and exit at anyplace (change from a variety of old paint styles to broad dashed white striping). If the HOV lanes had been tagged as a single way with change:lanes showing the restrictions on moving to and from the non-HOV lanes it would have been trivial to change the mapping to conform to the current paint. Mapped as separate ways you have to go back and remove the separate ways then the paint changes which is a pain.

When there is a solid line (I’ve seen white, yellow and a variety of parallel white/yellow versions of the “don’t change lanes here striping), there are generally designated areas for transitioning between HOV and non-HOV lanes. If you map the HOV as a separate way then you need to add any number of virtual cross over ways. I wondered why OsmAnd and Maps.me were always telling me to do slight rights or slight lefts in those areas until I looked at the mapping and saw the separate HOV lanes with virtual link ways connecting it to the non-HOV lanes. In essence putting in separate HOV ways where they don’t actually exist doesn’t always help the router.

FWIW, the JOSM plug-in that deals with change:lanes shows things nicely. And I suspect that routers like OsmAnd will be supporting it soon (if not already) as they support turn:lanes pretty well.

Extending this somewhat: I’ve traditionally mapped on and off ramps with the link leaving/joining the main way where the painted line becomes solid. With the relatively recent addition of change:lanes=*, I am wondering if the ramps should join the freeway at the actual physical point and the short lengths of acceleration/deceleration lanes which are physically part of the main traveled way be shown as another lane with change:lanes tagging to indicate where you are not supposed to cross.