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
_______________________________________________
Tagging mailing list
Tagging@openstreetmap.org
http://lists.openstreetmap.org/listinfo/tagging
