Re: [Tagging] Opinion on meaning of tracktype, smoothness and surface for routing

[André Pirard]

On 2014-03-20 15:29, Martin Koppenhoefer wrote : 2014-03-20 15:02 GMT+01:00 André Pirard <a.pirard.pa...@gmail.com>: Following a gentle dispute on OSM-talk-be about the class of a particular road, I pointed out without any follow-up  that road classification (primary ... tertiary, as well as national ... local on IGN maps) is very subjective but that the road width is very objective. yes, the highway classification is slightly subjective but as osm shows, the cloud can usually find a commonly accepted values, so this doesn't seem to be a real problem (also because it doesn't really matter if a road is classified as secondary rather than primary, and more than one class up or down is usually not the range up to discussion). The problem comes with such roads as Belgian N674 which is uniformly classified as national on IGN official maps. On the eastern part, it's worth the primary status for through, heavy traffic.  On the center part, it's certainly only secondary.  But on the part going NW it's a dangerous road. And, despite its official status, only its 5 m width and bends can show that : 2.5 m wide lorries can't cross each other and they step on the verge. The road once crumbled down into the meadow below and is waiting for the next turn. Even cars must break and make a brisk turn.  It would be nice that  OSM routing avoided that road. Of course everybody is free to add a road width as well, there is the tag "width" for this, and also the tag "lanes". Unfortunately until now, only 5% of all highway-elements (admittedly not only roads) have the tag lanes and 1% has the tag width. The width would come as a complementary information: avoid it despite a gentle official classification apparency.   Moreover, the width can be very easily measured with JOSM on Bing. you should be careful with the spherical mercator projection though, you might end up with different widths for the same width due to different latitudes, I am not sure how precise those measurements in JOSM actually are (some time ago they weren't but maybe this is fixed now). Good point that would have to be analyzed. Especially if there's a difference between NS and EW measurements! Of course, the closely related parameter is speed. related to width? I do not think there is a close relation, at least not a reliable one. Speed (to drive safely) is not intrinsic but in fact a consequence of other factors, including narrow width. Or it can be enforced. While reading your texts, I've had a crazy idea:  measuring vibration in the car. There are Android vibration measuring programs like Vibration Monitoring.  Alas, car vibration is very much dependent on car suspension.  But would some of us experiment this or another idea and come up with a solution? this sounds interesting indeed, while I agree that it mostly depends on the car suspension. With (unsuspended) bicycles this would be more reliable I guess, but still the ability of the driver / rider to avoid holes in the surface might make a huge difference (e.g. in Rome there are some very bad roads with profund holes that get tapped every now and then but later reopen due to the heavy traffic. If you are on roads that you drive often you almost automatically get the habit of avoiding them, also at higher speeds, because you know their exact locations by mind). Yes, dodging the suspension would be the idea, see next. On 2014-03-20 23:18, David Bannon wrote : If we wanted to measure vibration I guess we could have a process to calibrate individual car's suspension. Maybe something like driving over a set of steel pipes of defined size a defined distance apart ? Yes, I also thought of calibration, but the dynamics of suspension (spring + damper) is rather complex. The safest bet would be to stick 2€ accelerometers directly on the car axis. They're readily available for a cheap micro-controller called Arduino. This needs some software development compared to a ready made Android but it would be a fine project. On 2014-03-20 21:15, Fernando Trebien wrote : Even so, we would still have to presume things about the driver's personality (an adventurous person would not care much about rougher surfaces, while a precaucious one would probably rather avoid them). We can pick a "standard" personality (we don't even know that very well without some statistics, do we?) or we can probe other people and then apply statistics on the results. There would of course be a protocol such as driving at a 40 km/h constant speed and in straight line, unless, of course, it would break something, a fact that should of course intervene in the classification. On 2014-03-20 23:18, David Bannon wrote : However, I doubt if we'd achieve anything useful, the sort of roads we are talking about are usually quite erratic, smooth sections then substantial holes or what ever. You slow down for the holes or you break something ! But interesting idea.... Please note that, although it could also be used for local hazard warnings, my idea is to provide to routing software additional data with which it could favor one itinerary over another. Andre, I guess we can measure the width of a road to a reasonable accuracy via sat images. But I am not sure what that tells us. We cannot assume a relationship between width and quality of the road can we ? Not here in Australia anyway, many of the outback roads that are typical of the subject of this discussion are quite wide, wider than some of our fancy freeways closer to population centers. The width is only meaningful when the road is narrow and one must drive accordingly. You have plenty more room than we have. Here, the roads must at least pass between the people (and they're not hopping away) ;-) Cheers, André.

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