[OSRM-talk] Travel times too high

[Rudolf Mayer]

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