Hi,
After investigating two reports of OSRM routing failures around North
Tyneside, the common factor I can see is barrier=kerb tags added to
highway=crossing nodes intersecting highway=tertiary and
highway=cycleway/ footway ways.
Here are links to the two map note reports:
https://www.openstreetmap.org/note/2030228
https://www.openstreetmap.org/note/2030238
To investigate the report, I entered the postcodes given into the
default routing engine on the OSM map and found VERY odd routes going
10x the direct distance, and avoiding very obvious direct paths:
https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=55.0659%2C-1.4624%3B55.0511%2C-1.4530#map=14/55.0590/-1.4747&layers=N
Personally, I'd not noticed the OSM main map had added several routing
engines as I use separate tools, so have no idea how often the routing
engines update their database extracts but expect the issue to be
visible for a few days.
After two examples of bad routing, I checked the paths between the
geolocated points given and found one common factor - barrier=kerb on a
road / footway highway=crossing node.
https://www.openstreetmap.org/node/4341572135
My hunch is the router isn't familiar with barrier=kerb, so is assuming
BOTH ways are blocked and using an alternate path.
It is debatable how a routing engine should interpret highway=kerb tag,
however my own thought is the kerb is not on the highway=secondary - it
is on the highway=footway.
If anywhere, there should be two nodes on the footway separate from the
secondary to give information to wheelchair accessibility routers.
As an experiment, I've removed the barrier=kerb from a highway-crossing
and added two nodes on the cycleway, with the additional explicit tags of:
barrier=kerb
bicycle=yes
foot=yes
wheelchair=limited
kerb=lowered
tactile_paving=yes
horse=yes (ISTR UK law says cycle = horse!)
This is rather cumbersome compared with one barrier=kerb tag on the
node, but logic suggests this is more consistent with reality and
current routers.
Has any one used the barrier=kerb tag, or is familiar with the inner
workings of OSRM or similar engines please?
Thanks,
James
--
James Derrick
li...@jamesderrick.org, Cramlington, England
I wouldn't be a volunteer if you paid me...
https://www.openstreetmap.org/user/James%20Derrick
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