[Talk-us-massachusetts] Massachusetts Highway Classifications

[Brian M. Sperlongano]

Hello,

For those of you not following the recent discussions in talk-us and in
Slack, there has been considerable discussion about the current state of
highway classifications in the United States.  The currently documented US
guidelines[1] are based on physical road characteristics, rather than by
functional characteristics, which is how the highway classes are used in
the rest of the world.  This interpretation has resulted in exceptionally
poor map results[2] at low zoom levels, as through roads appear
disconnected because mappers have toggled highway classes along their
length based on changes in physical characteristics of the road.

[1] https://wiki.openstreetmap.org/wiki/United_States/Road_classification
[2] https://www.openstreetmap.org/#map=7/36.347/-97.236

I've been working with a group of mostly Northeast mappers (shout out to
aweech, Zeke Farwell, adamfranco, Rassilon, ZLima12, Kevin Kenny &
compdude) to develop new highway classification standards[3] that we're
hoping can evolve into replacement highway classification standards.  The
new guidelines that we've drafted emphasize road importance and through
connectivity, to ensure that map renders at lower zoom levels can
appropriately show long-distance road connectivity between population
centers.

[3] https://wiki.openstreetmap.org/wiki/United_States/Highway_classification

While developing these guidelines, we discovered that the MassGIS
"functional classifications" mapped quite nicely to functional highway
classifications, however, the "trunk" classification was under-used
compared to its place in the hierarchy.  This is likely the result of a
9-year old MassGIS road classification mapping which did not map anything
to trunk.  On review of the current mappings, we believe that the following
mappings make sense:

F_Class 2 -> highway=trunk
F_Class 3 -> highway=primary
F_Class 5 -> highway=secondary

In many cases, the mappings above are already implemented in the map, and
some would need to be changed.  There are a small number of outliers to
this mapping that we may want to consider documenting as exceptions, such
as local routes through Fitchburg and in the Plymouth area that are
probably more appropriately mapped lower than trunk.

In order to "try before you buy", we've stood up a temporary prototype
render[4] to demonstrate what the regional road network would look like if
we adopted these changes in highway classification.  This stripped-down
render shows only roads, boundaries, and city names, and is rigged to
suppress rendering of primary and below until higher zooms, so you can
better see the motorway/trunk road network.

The prototype render has implemented highway reclassifications for four New
England states only: NH, VT, MA, and RI.  In addition, Washington State has
also been reclassified in this prototype.  Note that these changes are ONLY
in this prototype and not in the live map at osm.org, and you can compare
the two maps side by side to see the difference.

[4] http://74.97.52.189:6789/openstreetmap-carto/#8/41.965/-71.084

Would the Massachusetts mapping community support adopting this MassGIS
functional class mapping, either with or without documented exceptions?
For anyone that wants to get involved with this effort more deeply,
collaboration is welcome, and we continue to discuss and work out the kinks
on Slack, in channel #local-us-northeast .

-Brian (ZeLonewolf)
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