[Tagging] new role for route relations: reverse

Johnparis okosm at johnfreed.com
Mon May 28 17:28:12 UTC 2018


I'm not sure exactly what you're describing or why a new role is needed.

If the bus traverses the way twice, once in each direction, you simply
include the way twice. "Magic turntable" is a good description. These are
fairly common in France, which (not surprisingly) has a lot of cul-de-sacs.

The bus ordinarily finds a way to turn around so the bus moves toward its
front, but I'm not sure it makes any difference to anyone what gear the
driver is using. First gear, second gear, reverse gear -- does it really
matter?

I conjured up two images before seeing Paul's "magic turntable" comment.
The first was a helicopter that winched the bus into the air and turned it
around. Again, what difference does it make to the mapper or consumer?

The second was an actual turntable -- the terminus of the San Francisco
Cable Car at Powell and Market. Nothing magic about it.

I have no problem with inventing a new tag (or role), but "reverse" sounds
too much like the deprecated (in PTv2) "backward" to me. Maybe
"reverse_gear"?

The best reason I can think of for this is to warn other mappers that
something oddball is happening here and so please don't assume that just
because there's no room for the bus to turn around, there's no need to
remove this way from the route. But that can be solved with a simple note=*
tag on the way.

John



On Mon, May 28, 2018 at 6:09 PM, Paul Allen <pla16021 at gmail.com> wrote:

> On Mon, May 28, 2018 at 3:40 PM, Erkin Alp G├╝ney <erkinalp9035 at gmail.com>
> wrote:
>
>> Does it have any stops in the street it reverses into?
>
>
> Not that I've seen.  But if somebody asked to get off there I'm fairly
> sure that most of the
> drivers would permit it.  And since it backs as far as a bench, I'm also
> fairly sure most
> drivers would let somebody sat on the bench waiting for the bus to board
> there.
>
>
>> If not, it is not formally a part of the route and just a convention.
>>
>
> Yes, but without it the route involves a role called "magic_turntable."
>
> If this were an end of route turnaround at a terminus then it's not
> mappable.  What
> happens when passengers are not on board and the bus is technically out of
> service
> are not part of the route.  But this is done with passengers on board in
> the middle of
> the route.
>
> Sure, renderers and routers might cope with the bus going to point X and
> magically
> switching its direction of travel by 180 degrees but it's a bit puzzling
> for data
> consumers.  Does the bus go out of service there?  Is it a terminus?  Has
> the mapper
> made a big mistake in the route?  Did some other mapper come along and
> accidentally delete part of the route?  Etc.
>
> Unless having role=reverse is going to cause big problems for renderers or
> routers I don't see any problem with having it.  I doubt it's going to get
> used
> often, so it's not a problem regarding data storage.  But I could be wrong.
>
> --
> Paul
>
>
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