[Talk-us] US highway classification

[Richard Welty]

On 5/29/11 11:59 AM, Anthony wrote:
> On Sun, May 29, 2011 at 11:44 AM, Richard Welty<rwelty at averillpark.net>  wrote:
>> On 5/29/11 11:37 AM, Anthony wrote:
>>> On Sun, May 29, 2011 at 10:34 AM, Richard Welty<rwelty at averillpark.net>
>>>   wrote:
>>>> in short: a routing engine will probably use classifications where
>>>> maxspeed
>>>> data is missing, but probably only to derive guesstimates of maxspeed
>>>> values.
>>> Now that I think about it, that's actually an excellent reason why
>>> classifications in the US should be by state.  Max speeds vary
>>> significantly by state, as well as classifications of what roads get
>>> what speeds.
>>>
>> actually, i'd argue that it's an excellent reason to start aggressively
>> collecting the missing maxspeed data.
> The two aren't mutually exclusive.
>
> Anyway, why argue about it?  If you have a reason to start
> aggressively collecting data the missing maxspeed data, just do it.
argue in the sense of a civil discussion of two distinctly different points
of view is not an unreasonable thing to be doing right now, we have a
bunch of distinctly different points of view and so far we're not entirely
uncivil about it (although sometimes pushing it a bit.)

here is the problem with the state by state classification trick. there's
been a standing effort do just that for a couple of years now:

http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed#United_States_of_America

as you can see, maxspeed data for exactly 3 states has been entered
in that time frame. i'd be tempted to call this effort a dismal failure.

there are two additional problems in addition to the obvious one that
the tables aren't filled out and seemingly won't be:

1) getting the routing engine authors to pay attention to this data

2) the sometimes tremendous variation between highways which default
and highways with speed limits that are at variance with these tables.
in surveying primaries, secondaries and tertiaries in Rensselaer County
(upstate NY) i frequently see explicit speed limits that are between
the default 55mph and the residential presumption of 30mph.

i really don't think there's any substitute for actually collecting
maxspeed for the network of major roads. sure, try a temporary
hack based on classifications, state-by-state if you want, but
i suspect that effort won't be very profitable.

collecting maxspeed, by comparison, while very tedious and time
consuming, goes directly to the issue at hand in routing engines.

and it also allows us to focus the classification discussion on making
"pretty" maps, which is probably where it should be focused.

and the distinction we're then discussing is a simple one:
classification as trunk based on physical characteristics vs
perceived function in the road network. the former is much
less subjective than the latter, but the latter does have its
passionate supporters. but i don't see the point in discussing
"major intercity routes" without a definition of what constitutes
an urban area that qualifies as an endpoint or midpoint.
that's why, for example, i'm not clear on whether NY 7/VT 9
from Troy, NY to Bennington, VT deserves trunk rather than
primary. at this point, i'd call it primary, but NE2 is sure it's
trunk (incidentially, i'd probably also upgrade NY 2->MA 2
to primary as well.)

richard