Re: [Talk-us] "System Continuity" in the Functional Classification network

[Bradley White]

> In this document is a concept called "System Continuity". In few words, a 
> roadway of a higher classification should not connect to a single roadway of 
> a lower classification, so the network remains interconnected.
> Do you know if this concept applies to OSM roads network also?

Motorway is purely a physical tag, so it does not necessarily follow
this principle. Primary, secondary, etc. should with few exceptions,
and usually do. Trunk, not so much. Most (probably) mappers in the US
use it to mean "expressway", and have arbitrarily varying cutoffs for
what constitutes as such, ranging from sensical (Santa Clara
expressway system, CA), to not so much (this U.S. highway has gone
from 5 lanes single-carriage to 4 lanes dual-carriage and thus has
become a trunk; this extremely important cross-country highway slows
down briefly through a small town and thus is no longer trunk).

Without getting too much into my opinions about this, the majority of
U.S. mappers use trunk to mean "almost a motorway but not quite", in
which case you will _not_ find continuity, while some U.S. mappers use
trunk to mean "most important roads that don't meet strict motorway
standards", in which case you will (or at least should) find
continuity.

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Re: [Talk-us] "System Continuity" in the Functional Classification network

[Greg Troxel]

Frederik Ramm  writes:

> Hi,
>
> On 07.09.2017 16:51, Max Erickson wrote:
>> Broadly speaking, yes, such continuity should apply. Maybe not using
>> exactly the same rule as the US DOT.
>
> I know this is talk-us and I won't attempt to say anything USA specific
> but such continuity definitely does not apply world-wide in OSM (there
> have been cases where people tried to enforce such continuity without
> local knowledge only to be repudiated by locals).

I also don't think there is a continuity notion in the US in OSM.

In particular, in the US, we have a notion of primary is a US highway
(or a state highway that is equally important).   So a continuity
property in OSM tagging tends to follow from continuity in the
underlying networks.

trunk, however, is special.  It more or less means "primary which is
50-90% of the way to motorway".  So that means there are stretches where
it changes, and that's ok.  (it shouldn't change every one mile, but 5
miles is defintely normal)



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Re: [Talk-us] "System Continuity" in the Functional Classification network

[Frederik Ramm]

Hi,

On 07.09.2017 16:51, Max Erickson wrote:
> Broadly speaking, yes, such continuity should apply. Maybe not using
> exactly the same rule as the US DOT.

I know this is talk-us and I won't attempt to say anything USA specific
but such continuity definitely does not apply world-wide in OSM (there
have been cases where people tried to enforce such continuity without
local knowledge only to be repudiated by locals).

Bye
Frederik


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Re: [Talk-us] "System Continuity" in the Functional Classification network

[Max Erickson]

Broadly speaking, yes, such continuity should apply. Maybe not using
exactly the same rule as the US DOT.

In practice there is an overfocus on observing how a given stretch of
road is built and an underfocus on the role it plays in the network.
My pet example is this stretch of US 2 & 41:
http://www.openstreetmap.org/#map=16/45.9090/-86.9901

Several times it has been upgraded to trunk, to reflect that it is
dual carriageway. But it doesn't make any sense for a trunk road to
run the short distance between a tiny village and a small town. Lately
I've been leaning towards classifying most of US 2 as trunk, as it is
the major east-west corridor in the region. But the difference between
primary and trunk should be for the longer stretch of road, not just
to distinguish that one stretch is overbuilt.

Another example I see in the data is short cul-de-sacs tagged as
tertiary, sometimes alone and sometimes as the continuation across an
intersection of a longer road. The sensible classification for these
is frequently unclassified, because they serve as the public access
road for a small commercial or industrial area.


Max

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[Talk-us] "System Continuity" in the Functional Classification network

[Ionut Radu - (p)]

Hi all,

I am researching Functional Classification in Detroit counties and I found a 
pdf from US Department of transportation - FHA entitled Highway Functional 
Classification: Concepts, Criteria and Procedures. (if someone is interested 
here's the link: 
http://www.sddot.com/transportation/highways/classification/docs/HwyFunctionalClassification.pdf)
In this document is a concept called "System Continuity". In few words, a 
roadway of a higher classification should not connect to a single roadway of a 
lower classification, so the network remains interconnected.
Do you know if this concept applies to OSM roads network also?
I would greatly appreciate your feedback.

Some IDs as an example:
way 59511836
way 506656034
way 506656035
way 491105399
way 42372800
way 507025566
way 8697917
way 40788309
way 435476888
way 45806340
way 506710300

Best regards,
Ionut

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