[Talk-GB] barrier=kerb on highways may be blocking OSRM (Car) routing

[James Derrick]

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
     lists at jamesderrick.org, Cramlington, England
     I wouldn't be a volunteer if you paid me...
     https://www.openstreetmap.org/user/James%20Derrick