[Talk-us] Prioritizing multi-banded route designators (multiple overlaps) on ways: the "Principal route designator" concept

[Peter Davies]

I think it useful to spin off this topic from the long and still unfinished
debate about directional roles in relations.  I hope it can be agreed more
quickly than the cardinal directional roles issue!

The question is how to handle US roadway routes that are double, triple or
even quad-banded, having multiple route designators.  Some OSM mappers call
this topic "route overlaps."  I might call it "information overload." On
most maps, renderers simply show ALL the shields. But is it helpful to have
roads peppered with conflicting information about the route number?  Who
gains by knowing that Western Avenue, Augusta, Maine is US 202, ME 11, ME
17 and ME 100?  Isn't this really confusing and unhelpful for most map
users?

Now, if it's confusing on a map, just think how confusing it is in a
navigation system or a traffic event info system.  "Look out for a crash on
US 202 eastbound / ME 11 northbound / ME 17 northbound / ME 100 eastbound
(Western Avenue) in Augusta."  We need to know which route designator is
the most important one, and to use mainly or only that one when talking to
drivers.

This is not something that OSM needs to make up. The principal designator
should the top shield, left shield or top-left shield on traffic signs.
State DOTs and police also face this same problem, and every multi-banded
route section in states with which I work already has an "official"
principal designator.  We need a way of capturing this in OSM for use in
nav systems and info systems, as well as (perhaps) for ridding simple maps
of route shield clutter.

Martijn van Exel and perhaps others have suggested that we should use only
relations to define route designators on ways, and not way ref tags.
 However  I can't see how the relations alone can indicate this hierarchy
of route designators on a way.

As an example, let's look again at Augusta, ME, where Western Avenue is
quad banded as US 202;ME 11;ME 17;ME 100.  I've just listed these routes in
the logical "highest system, lowest number first" sequence.  I see that the
current OSM way ref tag by the Senator Inn (just east of I-95) only says US
202, though I know from visits and from working with MEDOT that all four
shields exist on the ground.  The OSM relations currently include all four
of the routes, but do not help us to prioritize the designators.

To check out what MEDOT and the State Police think about Western Avenue's
principal designator, I just logged into Maine's state CARS system
(Condition Acquisition and Reporting System -- which we build and maintain
for MEDOT here at Castle Rock) and it suggests that Western Avenue is "top
posted" for MEDOT users as ME 100, not US 202.  Of course I then looked at
Google.  No, I'm not going to copy it.  But this is fair usage, I think,
for research on this general problem. Google says Western Avenue is ME 100
or ME 11 on Streetview.  But the Google Map shows all four shields.

I currently believe that Western Avenue "officially" has ME 100 as its
principal designator, and not the apparently "higher classification" US 202
route designation.  However, the signs have US 202 at the top left of a
"square" of four shields.  So I personally I would continue to treat this
road as principally US 202 in OSM, replacing the present way ref tags that
say "US 202" with "US 202;ME 11;ME 17;ME 100".  But in doing so I'd be
adding to map clutter unless we build simple info systems that focus only
on the first named (principal) route designator.

I guess a more simple solution (always worth considering!) would be to use
the way ref to show ONLY the principal (first) signed designator, and to
cover the secondary route designations using the relations. This would
avoid info info duplication between ways and relations (at least on
multi-banded ways), and would automatically clear up map clutter of
confusing shields on most OSM based maps.  Those who care about all the
secondary designations could get them from the relations.  We could "keep
it simple and stupid" for drivers.  The way ref would convey only the
"Principal route designator."

There are other examples of the idealized "highest system, lowest number"
rule not being used. I 35 and I 80 north and west of Des Moines IA have the
principal designator "I 80", not "I 35". I 80 determines the milemarkers
and the exit numbers on this common section.  Looking at the milemarkers
(and exits, on freeways) is one way in which OSM mappers can determine the
state DOT's principal route designator.

****

Finally as an aside, I think the OSM (bad?) habit of missing off the "US"
or "I" or "ME" classification in relation (but not the way) refs perhaps
means we don't know that Western Avenue is US 202 (as against ME 202)
unless we look at the way ref as well as the relation ref.  Currently I
don't think the relation ref alone can tell us the type of shield on which
the route number is written.  I believe it would be better if relation refs
and way refs were written consistently, as US 202 (etc.) and not just 202
as we currently see in relation refs.

Peter



On Thu, Dec 5, 2013 at 9:20 AM, Martijn van Exel <m at rtijn.org> wrote:

> Richard - true. It's sort of a chicken vs egg situation. As long as
> there is no clear use case for one or the other, both practices will
> remain in use. That's why I was so excited to see work continue on the
> shield rendering which uses the refs on the relations. As I mentioned,
> at Telenav we also pretty much solely rely on the relation refs for
> the route numbers (and the relation member roles for the cardinal
> direction, if we can come to a consensus about that.) These things may
> help us converge on one way of doing things.
>
> On Sat, Nov 30, 2013 at 3:09 PM, Richard Welty <rwelty at averillpark.net>
> wrote:
> > On 11/30/13 4:57 PM, Paul Johnson wrote:
> >
> >
> > On Sat, Nov 30, 2013 at 12:57 PM, James Mast <rickmastfan67 at hotmail.com>
> > wrote:
> >>
> >> Peter, it would just be for the relations.  It would stay the current
> >> status-quo for the ways using at all times the "ref & unsigned_ref" tags
> >> (see I-394 example below).
> >
> >
> > I can't wait until we can finally kill this dinosaur.  Refs, as they're
> > presently tagged on ways, almost always apply to the route instead of the
> > way.  And not to mention they're just a pain in the butt to maintain
> > properly where multiplexes exist, something that works cleanly in
> relations.
> >
> > we're kind of stuck with ref on the ways until the data
> > and data consumers come up to speed. there are a lot
> > of route relations still to be built in the US.
> >
> > richard
> >
> >
> >
> > _______________________________________________
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> >
>
>
>
> --
> Martijn van Exel
> http://oegeo.wordpress.com/
> http://openstreetmap.us/
>
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