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

Alex Mauer hawke at hawkesnest.net
Tue Mar 4 16:26:19 GMT 2008

Karl Newman 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?

Dual carriageway, higher speeds.  Built similarly to a motorway, but 
without the restricted access.

>     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?

As far as I know from the history of OSM unclassified and residential 
are basically the same, and they render the same in pretty much every 
renderer.  I believe it's a historical artifact where "residential" 
pretty much meant "unclassified+abutters=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.

Other roads change speed as they enter urban places (e.g. primary roads 
may go from 55 down to 25 to pass through a hamlet)  Why shouldn't 
tertiary be the same?  It's all about the relative status of a road to 
the roads around it.

>     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.

Hmm...it seems to me that perhaps you're writing this from a perspective 
of "what a driver using the road might expect", while I'm coming from a 
perspective of "how should this road be tagged".  Is that the case?

-Alex Mauer "hawke"

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