[Talk-us] Relation member order/structure: Why don't we do it in the road?

Peter Davies peter.davies at crc-corp.com
Sun Jan 12 19:29:19 UTC 2014


Andrew,

I'm not so keen on route relations either.  In my view they are
duplicative, complex, confusing and costly to code. As a UK
traffic engineer I'd much rather that my US State DOT clients dropped the
practice of multi-banding many roads, so that each way would have one and
only one definitive ref, as is the case in most other countries.

Why? Drivers are not helped by sign clutter. It's a lot like texting.
 Messy signs are dangerous and distracting. The same is true for nav
systems, info systems and maps. Less is more.  Keep it simple.  This is
what the safety research shows.

In practice most US states already use the first-posted route designator
when fixing milepoints and motorway exit numbers, and I've asked OSM
mappers to list this first in the way ref. Then the other signed and
unsigned designators already follow for each way, using the infamous ";".
 Once that's been done, the relation carries almost no additional
information.  It doesn't even help us to assemble the ways as there is no
consensus on the sequencing order of ways in the relation, for complex
routes.

Is there another "way" forward?  Why don't we do it in the road?  (Thank
you, John Lennon.)   A radical way to solve the ragged discussions of these
past 3 months could be to put the posted cardinal direction on the way, as
well as the ref(s).  An example could be "ref=US 202:east;ME 11:north;ME
17:north;ME 100:east" replacing a relation at least 100 times longer, full
of complex data structures that are highly prone to error.

But here we violate  the 1 tag, 1 value rule even more than at present.
 Another way to "do it on the road" could be

ref=US 202
alt_ref:1=ME 11
alt_ref:2=ME 17
alt_ref:3=ME 100

This could satisfy those EU nations who hate the current US practice of
packing multiple values into one.  A bot could probably be written to
unpack every US way ref tag and rewrite it in the form shown above.  In
many case it would be just "ref=I 80" "alt_ref=US 6".

A major benefit would be to bring the US back into compliance with the rest
of the world, for example with the A4 past Amsterdam's Schipol Airport,
which has "ref=A4"
"int_ref=E 19".

There are already 914 alt_ref tags in use, worldwide.  A US bot could
swiftly make it millions.  The relations labour of love could continue, but
without holding up this year's system deployments.

If we then took one extra step we could capture the posted cardinal
directionality on the way as well:

ref=US 202:east
alt_ref:1=ME 11:north
alt_ref:2=ME 17:north
alt_ref:3=ME 100:east

Oops, now I've upset all of Germany AND America.  So how about

ref=US 202
alt_ref:1=ME 11
alt_ref:2=ME 17
alt_ref:3=ME 100
posted:1=US 202:east
posted:2=ME 11:north
posted:3=ME 17:north
posted:4=ME 100:east

Posting route confirmation signs and junction signs is really a separate
matter from route designation.  German autobahns use "destination=Berlin"
in the way that Americans use "posted=US 202 east", so why try to combine
all these separate functions into a single ref tag?

For two-way roads like the Augusta, Maine, case (Western Avenue, off I-95),
it *could *become:

posted:forward=US 202 east
posted:forward=ME 11 north
posted:forward=ME 17 north
posted:forward=ME 100 east
posted:backward=US 202 west
posted:backward=ME 11 south
posted:backward=ME 17 south
posted:backward=ME 100 west

OK, so this is long, but very few ways are quad-banded.  Also the backward
posting can be inferred from forward in 99.9% of cases.  It's only really
needed if we have:

posted:forward=Muskogee Turnpike south
posted:backward=Muskogee Turnpike east

which is *extremely *rare.  I think Paul Johnson will let us know if he can
definitely find it in Oklahoma.

Time to get it done and just "do it in the road?"

Peter



On Sun, Jan 12, 2014 at 4:27 PM, Andrew Hain <andrewhainosm at hotmail.co.uk>wrote:

> Peter Davies <peter.davies at ...> writes:
>
> > Does anyone know if the Europeans (of which I'm one, oops) have any plans
> to create route relations?  I have found none while in UK, NL, D, A, CH, I
> and F this past two weeks, but perhaps I didn't look hard enough.
> >
>
> Route relations for roads have occasionally be created in the UK but many
> mappers are not keen on them.
>
> http://thread.gmane.org/gmane.comp.gis.openstreetmap.region.gb/6235
> http://thread.gmane.org/gmane.comp.gis.openstreetmap.region.gb/6731
>
> Feel free to argue against from an international or any other viewpoint of
> course.
>
> --
> Andrew
>
>
> _______________________________________________
> Talk-us mailing list
> Talk-us at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-us
>
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