[Tagging] access=emergency revisited

Richard Welty rwelty at averillpark.net
Fri Nov 23 00:45:25 GMT 2012


On 11/22/12 7:33 PM, Greg Troxel wrote:
> Reading over your comments about turn restrictions and the NY state
> code, I feel like we will end up with tortuous reasoning and miss the
> mark.  Stepping way back and ignoring legal details, it seems like we
> need a schema to express what kinds of people/vehicles/etc. may do what,
> and a way to use that data in routers.  An important case is
> transforming OSM data to GPS receivers, especially Garmin, and another
> case, which will perhaps become dominant, is a purpose-written program
> (e.g. for Android).
the current implementation of no u-turn in JOSM is actually pretty clean to
use and is an accurate model of the real/legal situation. it even builds
the emergency access right into the turn restriction.

the question you bring up about the translation to GPS is exactly the
important one. i need to talk to the folks who do mkgmap about what
they handle. it's possible this may be targeted at a different GPS brand,
and i'll jump off that bridge when i come to it.

i'm not presuming the presence of a working emergency mode in the GPS.
there are enough issues that i suspect i'll be generating somewhat
customized maps. in particular, there are different classes of equipment
in firehouses with wildly differing weights, turn restrictions, and heights
and there's a fair chance i'll have to build pumper maps, hook-and-ladder
maps, extensible ladder truck maps, and so forth. that's all stuff for what
i'm currently generically referring to as "local policy files".
>
> I'm left with wondering about how to distinguish what's physically
> possible with what's prohibited.   I know of one intersection (Mass Ave
> and Memorial Drive in cambrige), where heading east on Memorial Drive,
> there is an underpass, but if that isn't taken, you can turn right on
> Mass Ave, but you can't go straight or left because of jersey barriers.
> (I've seen people try, and dialed 911 for it many times....)   Now, an
> ambulance could turn left, drive the wrong way on the one-way half of
> the street, and recover to the right after getting beyond, but that's
> a bit different.  So I guess if the geometry reflects what is possible
> and the turn restrictions reflect what's prohibited but possible, this
> works.
right, and since in some states (if not all) authorized emergency 
vehicles are
authorized, among other things, to ignore all turn and oneway restrictions,

> I hope this qualifies for not trolling :-)
i'm not complaining.

richard




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