On Sat, Oct 27, 2012 at 01:45:42PM +0200, Michel Schinz wrote:
On Thu, Oct 25, 2012 at 12:32 AM, Sarah Hoffmann lonvia@denofr.de wrote: [...]
Try it out and let me know if you have suggestions to improve the profiles.
So, I played a bit more with your router, and have two remarks:
- In "bike" mode, one-way restrictions are ignored, and while this
may correspond to the riding style of some people, it can produce some quite dangerous routes... One example is the following one: http://osrm.at/1Br If you switch the profile to "car", you'll see that the route changes to avoid going against the trafic in the "Rue des Parcs" (a very dangerous thing to do given how busy the area is).
Good catch. Fixed.
- In "bike" mode, it seems that the router considers everything
tagged with "highway=path" as a potential route, and this can lead it to suggest some really tricky routes. One example is the following one: http://osrm.at/1Bs The path that starts at the information sign ("i" on the map) and then goes through the forest is not suitable at all for biking. While doable on a mountain bike, this path is completely unsuitable for normal biking: it's a steep single track with a few parts that are tricky to negotiate.
highway=path is a nasty tag because it can be anything from a dedicated cycleway down to a path only suitable for climbers with gear. Completely excluding them would be too strong, so some heuristic is needed which ones to include. Using sac_scale seemed a good idea to exclude at least the worst paths but I'm open for other suggestions. Are any other tags in frequent use that mark paths as unsuitable for bikes? Should we invent one, bicycle=mtb for example?
Another possibility would be to come from the other side and only include paths tagged with bicycle=yes or bicycle=designated. That would be also a rather strong assumption and currently exclude a lot of good paths as well but it would put routing on the safe side and with time people would get the habit of marking the ways correctly.
I don't really have a good suggestion for this second problem, but maybe having separate profiles for road and mountain bikes would be a good idea. The profile for road bikes would take only paved roads, while the one for mountain bikes would consider unpaved roads/paths too. There could also be a third profile (for city bikes, or what we call "vélos tous chemins" in French) that would consider unpaved but easy paths as valid, but I fear that this is very hard to do without an improvement in the tagging of the paths and/or information about the terrain.
Yes, I've considered offering two profiles already. I wouldn't go as far as having a profile for mountain bikers but at least paved vs. unpaved seems a good idea. For the foot profile as well btw.
I'll look into it next week.
Sarah