I would like to tell you about another small project I will be working on for the next months. It is made possible by a NLNet NGI Zero Discovery grant:
Inferring default speed limits for situations where concrete
maxspeed information is missing. Last time I checked, only 12% of roads had this tagged at all and while the number of roads tagged with
maxspeed of course is increasing, so is the number of roads.
highway=unclassified, it looks pretty much like a zero sum game.
This means, that not only did OSM based router software always have to fill huge holes in data to produce reasonably precise ETAs (etc.), it is also not something that will get any better on a global scale in the foreseeable future.
Why so sketchy?
It’s also understandable why the data is so sketchy: Roads can simply be traced from satellite imagery. Finding speed limit signs on the other hand often requires to look for them on-site or via good Mapillary / KartaView coverage which is in itself already much more time-intensive. Not only that - it’s even more time-intensive to confirm that there is no signed speed limit for a given segment of road as the speed limit sign could be located all the way down the road. (One reason why the speed-limits quest is disabled in StreetComplete.)
Finally, if it turns out there is no sign, tagging the correct
maxspeed requires knowing the traffic legislation in the country one is mapping in. (And sometimes one errs in what one thinks is correct. Did you know that the default no-speed-limits in Germany are technically are not limited to the Autobahn?)
So, the goal is to get the OSM based routing engines to use this data in order to improve the routing precision (by filling the holes in the data), but also for other modes of transportation than just cars. (Nobody maps
maxspeed:hgv unless there is a sign.)
Since I am not the maintainer of either of those, at least the goal is to lower the (implementation effort) bar for them a lot. We’ll see.
What I will be working on specifically in the frame of the NLNet grant is to
review and try to complete this wiki page that (shall) contain all the legislative data regarding default speed limits I started years ago
complete and debug this parser that was started by Ian Wagner from StadiaMaps for that wiki page that outputs an easy to parse JSON
write a reference implementation that, given a set of tags and a country, determine the default max speeds (for the different vehicle types) using the data from that JSON. I’ll probably write
write a small simple web tool on which to try it out
State of the Map
Finally, I will also hold a talk at the State of the Map 2022 in Florence about this. I hope I have something to show until then 😅 🤞