[Talk-us] "highway" tags in the US

Karl Newman siliconfiend at gmail.com
Tue Mar 4 14:57:28 GMT 2008

On Tue, Mar 4, 2008 at 1:24 AM, Alex Mauer <hawke at hawkesnest.net> wrote:

> Karl Newman wrote:
> > Okay, for trunk, how about *mainly* ramp access, with grade-level
> > crossing access to side roads permitted, but without traffic controls on
> > the highway where they meet?
> Hmm, I don't think the ramp access should be a requirement.  Agreed on
> "without traffic controls on the trunk highway at intersections" though.

I said mainly, not all. Otherwise, why wouldn't you just make it primary in
that case?

> I can think of two highways in my area (central Wisconsin) that fall
> under this; both are state highways.
> > Re: County roads as secondary, I was thinking mostly of speed limits as
> > a guideline for the classifications. There aren't a whole lot of
> > numbered county roads here in California, so I don't have much to judge
> > them by.
> Around here the county roads vary widely in speed limit, anywhere from
> 30 to 55 mph.  They all seem to be two-lanes (total, not per-direction),
> with fairly narrow shoulders.

My guidelines are thinking about expectations, as well. What you say about
county roads basically says that you have to lower your expectations about
them, because you don't know what the road is going to be like or how fast
you'll be able to travel it.

> > So you would place unclassified above tertiary? I haven't spent much
> > time looking at road classifications when I've been in Europe (I
> > probably would now since I've joined OSM), but that seems to go against
> > the existing guidelines.
> No...I use tertiary as you describe "missing_tag":
> "residential branch roads which are main roads
> through subdivisions..." though, I don't see why it should be exclusive
> to residential/subdivision areas.
> I noticed now there's also a difference in your usage of unclassified;
> As I use them, these are ordinary, unremarkable roads; if they were in a
> residential area, they'd be highway=residential.  So I put
> "unclassified" down a level from where you do, in between your
> missing_tag and residential.

Then why should we even distinguish between unclassified and residential?

> The first part of your description of unclassified seems to fit there,
> as well: "urban commercial district or rural low-density housing..."
> I suppose we differ in that I feel that tertiary can scale: in a
> residential area, it's the "main roads with fewer driveways", in a
> commercial or industrial area, it's the main roads as well, and in rural
> areas it's main roads which are not county highways.

I think it's not so good to make the tertiary tag cover all those cases. As
you've described it, in a residential neighborhood, that road is generally
25 MPH, in a commercial or industrial area it's usually 35 MPH, and in a
rural area, 40-55 MPH. I think only last one makes sense.

> I would not use "direct driveway access" as a factor for distinguishing
> highways.  Roads of all classifications except motorway may have direct
> driveway access, especially in rural areas.

It's just a guideline, and it goes toward expectations. Driving down a
residential street, I expect to have to watch carefully for kids playing or
for drivers backing out. I realize that almost any road can have direct
driveway access, but it's very infrequent (more like every 1/4 mile at
least, not every 100 feet as in a residential neighborhood). On a more
heavily-traveled road with a higher speed limit, the driver pulling out has
to be more careful than the through traffic.

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