Hi Stefan!
On 2014-05-19 09:47, Stefan Göckeritz wrote:
since some weeks I experience calculated travel times that are way
higher than they are in reality.
I use OSRM for quite some time now, but since the durations are not
exact I use Google Maps, just because I need more exact travel times.
For instance traveling from Berlin to Bonn takes 7 to 8 hours according
to OSRM.at.
Google Maps states something around 5 hours which is appropriate as I
can say from my experience on this route.
What is the deal with the time, they used to be not that exact, but
since some time (I can't actually say since when) the calaculations are
worse.
Has there been a major change in computation or the car profile?
I noticed that also a few times, and there was a similar discussion
started by me, see
https://lists.openstreetmap.org/pipermail/osrm-talk/2014-March/000462.html
Currently it seems that the car profile is currently asuming as default
value 90kmh for a motorway
(https://github.com/DennisOSRM/Project-OSRM/blob/master/profiles/car.lua)
From that speed, it seems only 80% are assumed as average driving time.
It seems that the profile does honour max_speed settings
(https://github.com/DennisOSRM/Project-OSRM/blob/master/profiles/car.lua#L173),
but it still means that e.g. for an Austrian motorway, 104 km/h (of
130km/h) is the assumed average, and that seems just too low.
I guess assuming around 80% of average speed can be ok for
highways/roads that have only one lane, have crossings & lights, but for
motorways with 2+ lanes and without any level crossing, it seems just
too much.
For your specific route, my mod in the interface that also displays
travel time for each segment
(http://kronos.ifs.tuwien.ac.at/osrm/main.html?loc=52.517037,13.388849&loc=50.735849,7.101081)
shows that you spent a lot of time with this:
Continue onto A 2 411 km (5 h 38 min | 72.7 km/h)
So I guess the issue is
- there's no maxspeed tagging (because you have no maxspeed for the
motorway in that section :-))
=> thus OSRM assumes speed to be 90km/h, from that it takes 80%
=> you get the 72km/h as average..
(maybe the slightly higher value is from some portions where there is a
maxspeed set.)
And I assume in fact if the road is free you go double that speed...
So, I guess a few things that could be improved
- If maxspeed=<NIL>, and "in germany", assume something like at least
130kmh.. That shouldn't be that difficult to achieve.
- rethink if 80% on a highway with status motor_way and/or lanes>=2 is
really appropriate. I'd assume something ~90-95% to be more reasonable
on a motorway.
Greetings
Rudi
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