Jo, a can of worms ? I hope it , this mailing list is too quiet :-)
Wouter, While I understand that for routing one does not need the separate cycleways, I don't see much difference in a router that sends me over the N47 with separate cycleways (illegal in your eyes) or without separate cycleways (ok for you). The possible problem with a badly connected separate cycleway, is that a GPS with very high precision, won't let me make the second left turn into Baan nr. 90 So as long as the N47 is not tagged with bicycle = no, there won't be any problem IMHO But as you wrote, you get the same result with less work by putting tags on the main road. regards m On Tue, May 13, 2014 at 10:34 AM, Wouter Hamelinck < [email protected]> wrote: > OK, I'll bite about the cycleway. > > Go a bit south and you will see something called Macharisdreef and > something called Baan nr. 90. Imagine you want to cycle from > Macharisdreef to Baan nr. 90 along that N47 and use only the map data > as a routing algorithm would do. > * First attempt: well it is obvious, you just take the cycleway at the > east of the N47 to cycle from the one to the other. Shortest, lots of > cycleway, it looks perfect. Reality: this is illegal, you only can > follow that cycleway north, otherwise you cycle on the wrong side of > the road. So we have to correct the data. Let's say we put a > oneway=yes on the eastern cycleway. > * Second attempt: well obvious again, you simply take the N47 instead > of that cycleway. Only slightly longer, a bit less attractive, but not > too bad. Reality: this is illegal. There are cycleways, you have to > follow those. So we have to correct the data. Somehow we have to make > explicit that you are not supposed to cycle on the N47 but have to > follow the parallel cycleways. So let's put some tag explaining that > on the N47. I don't really care which one. It could be boldly > bicycle=no or the proposed bicycle=use_sidepath or whatever. I'm just > not supposed to cycle over the highway=primary. > * Third attempt: let's see. When leaving Macharisdreef, I have only > two options. Either I take the N47, but that is illegal, or I take the > cycleway east of N47. Nothing else connects to Marcharisdreef. So my > only option is to follow the eastern cycleway to the north. Hmm, I > then can cross the N47 right before that terribly complicated junction > and start following the western cycleway. Until I find a place to > cross the N47 again. The first one that I find is right at the > roundabout about 500m to the south. There, I can traverse to the > eastern cycleway and follow that north to Baan nr. 90. OK, I have a > solution. Not exactly short (about 1km instead of the 50m in my > previous attempts), but at least it is legal. Reality: not entirely > legal (at least at the roundabout you should go around it instead of > traversing before the roundabout), but close enough for me. With the > slightest bit of common sense I wouldn't follow that anyhow. What I > would do is traverse N47, follow the western cycleway and traverse > again when I am at Baan nr. 90. Why didn't the algorithm propose that? > Simple: the road to the east of N47 are not connected to the western > cycleway and vice verse. So we have to modify the data again. At every > point where there is a sideroad from only one side we need to add a > short cycleway to connect the cycleway on the other side with the > junction. > > Once those junctions are made, I will get the obvious, correct route. > > Conclusion: lots of work and near impossible to maintain. > > Now, let's see what happens if I tag the cycle paths on the > highway=primary in stead of drawing them separately. It is in any case > a lot less work. No need to draw the separate cycleways and no need to > add all the technical tags on both highway=primary and > highway=cycleway that I described previously to get correct results. I > just add cycleway=lane or something similar to the highway=primary. > What does the algorithm say? I will just say: "At the end of > Macharisdreef turn left on N47. I know there are are cycle lanes so > you should follow those instead of cycling in the middle of the road. > And after 50m you turn left in Baan nr. 90.". > Simple, clear, robust. > > That is why I only will draw separate cycleways if there really is no > other option. Even if it is not wrong to draw to the cycleway > separately, it is just a lot of work, impossible to maintain and a > huge source of errors waiting to happen. > > Bonus question 1: what happens with routing for pedestrians in both > situations? > Bonus question 2: in how many ways is it possible to make mistakes > when mapping cycling routes? Especially the case of a route that can > be followed in both directions is enlightening. > Bonus question 3: which situation has the least tags (=lowest database > size) and the least junctions and ways (=greater efficiency for > routing algorithms like Dijkstra)? > > wouter > > On Tue, May 13, 2014 at 9:16 AM, Jo <[email protected]> wrote: > > We have more recent AGIV imagery now. All I see wrong is that the > cycleway > > is connected to the underground waterway. But the main road is too. > Probably > > to silence validator warnings in a totally inappropriate way... > > > > I still think it's correct to draw the cycleways separate cases like > this. > > > > Marc, you opened a can of worms there :-) But it's good that the subject > of > > using separate ways to represent lanes is brought up on the list. > > > > Jo > > > > > > 2014-05-13 8:15 GMT+02:00 Wouter Hamelinck <[email protected]>: > > > >> Wow, based on the Bing images a simple T-crossing and a bypass is all > >> there is in reality. > >> Also, note the nice examples of about everything that can go wrong > >> when drawing parallel cycleways along the N47. > >> > >> wouter > >> > >> 2014-05-13 6:35 GMT+02:00 Jo <[email protected]>: > >> > Zeker wel, het klopt niet om een aparte weg te tekenen voor elk > rijvak. > >> > > >> > Absolutely, using a separate way to represent traffic lanes is not how > >> > it's > >> > supposed to be done. > >> > > >> > Jo > >> > > >> > > >> > 2014-05-13 5:48 GMT+02:00 Marc Gemis <[email protected]>: > >> >> > >> >> Hallo, > >> >> > >> >> Ik vraag me af of het OK is het volgende kruispunt te vereenvoudigen > >> >> via > >> >> turn:lanes : http://osm.org/go/0Ejo5_fqb--?way=51738440 > >> >> > >> >> I wonder whether it's ok to simplify the following crossing with > >> >> turn:lanes tagging: http://osm.org/go/0Ejo5_fqb--?way=51738440 > >> >> > >> >> met vriendelijke groeten > >> >> regards > >> >> > >> >> m > >> >> > >> >> _______________________________________________ > >> >> Talk-be mailing list > >> >> [email protected] > >> >> https://lists.openstreetmap.org/listinfo/talk-be > >> >> > >> > > >> > > >> > _______________________________________________ > >> > Talk-be mailing list > >> > [email protected] > >> > https://lists.openstreetmap.org/listinfo/talk-be > >> > > >> > >> > >> > >> -- > >> "Den som ikke tror på seg selv kommer ingen vei." > >> - Thor Heyerdahl > > > > > > > > -- > "Den som ikke tror på seg selv kommer ingen vei." > - Thor Heyerdahl > > _______________________________________________ > Talk-be mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-be >
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