[OSRM-talk] Fixing routing with tags

[Daniel Patterson]

If you're into reading data analysis studies, this paper is a fun read:

> Which quality is a route? A methodology for assessing route quality using
spatio-temporal metrics
https://onlinelibrary.wiley.com/doi/abs/10.1111/tgis.12705

It focuses on driving routes, and proposes an approach for comparing routes
to determine which one is "better".  You could certainly use it to tune
weights in the model to produce "high quality" routes that fit your
criteria for "high quality".  But as Richard points out, there's no
one-size-fits-all answer.

I do think there are improvements OSRM could make - more heavily favouring
the road hierarchy is a big one that I think would help a lot in the
absence of traffic data.  PRs welcomed!

daniel

On Wed, Dec 13, 2023 at 1:56 AM Richard Fairhurst <richard at systemed.net>
wrote:

> Florian Lohoff wrote:
> > The route uses "Im Kracht" where it should stay on K22 and L775:
> > [...]
> > The route uses "Westerweg" but it should stay on K27, L876, L803:
> > [...]
> > So my idea would be to create a tag like **relative_route_cost=**
>
> First, you seem to be assuming that "fast car routing" is the only sort of
> routing. It really isn't. If you're riding a bike then going via quieter
> roads like Westerweg or Im Kracht is greatly preferable:
>
>
> https://cycle.travel/map?from=&to=&fromLL=52.234035,8.513781&toLL=52.238110,8.483742
>
> https://cycle.travel/map?from=&to=&fromLL=52.280323,8.696529&toLL=52.289005,8.709464
>
> Second, this is trivially fixable. As Nils says, you just change the
> routing weight of minor roads and/or add a greater turn penalty when
> turning off a major road onto a minor road.
>
> Routing engines are opinionated. There is no single right or wrong answer
> for "the best route from A to B"; they each have their own preferences.
> Those preferences can be tweaked. What you seem to be advocating is a tag
> in OSM for "roads Florian likes to drive on", but at that point we also
> need one for "roads Richard likes to cycle on" and so on, and that's going
> to get very messy very quickly.
>
> I note that, in the second example, Google Maps also chooses a quieter
> road (though in this case Wittekindstraße rather than Westerweg). Google
> Maps (and Waze, and Apple Maps) using minor roads to save a few seconds is
> a massive issue, and has caused traffic authorities in the UK and elsewhere
> to spend millions putting up bollards to block former cut-throughs. But the
> way to fix that is not to break the map data, the way to fix it is for
> routing engine developers to be responsible citizens. (Google? Good luck
> with that.)
>
> FWIW, I'm not convinced that it's possible to do good quality car routing
> on OSM data without external datasets, principally traffic. (The situation
> with cycling and walking is slightly different.) The engines featured on
> osm.org are essentially tech demos for testing connectivity and
> demonstrating a use of OSM data, but they won't give you the best
> real-world results.
>
> Richard
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