[OSM-talk] Cycle lanes

[Cartinus]

On Monday 24 March 2008 14:01:59 Ben Laenen wrote:
> On Monday 24 March 2008, Andy Allan wrote:
> > I think a lot of the physical cycleway tagging is ambiguous at the
> > moment, especially with the cycleway= tag. I think cycleway=track was
> > intended only for adding to highway=* (not highway=cycleway), but I
> > would advise that all off-road cycle paths, including those on
> > sidewalks, are drawn as a separate way with highway=cycleway instead.
>
> I beg to differ here. When you have to tag cycleways belonging to a road
> not as "highway=whatever, cycleway=track" but as
> separate "highway=cycleway" they just become an editing mess,
> especially at intersections. Especially when adding route relations to
> them. Just imagine two dual carriage ways with on either side a
> cycleway crossing: you then need 24 different ways to just represent
> that one intersection, like this:
>
>
> --++++-- cycleway
> --++++-- road
> --++++-- road
> --++++-- cycleway
>
>
> But there are more reasons why I don't like these as separate highways:
>
> * We're also not tagging sidewalks as separate "highway=footway" right
> (well, I guess there is not tag for sidewalks yet but it'll come -- but
> I can't imagine someone tagging them all like separate ways anyway,
> just think about the intersection mentioned above and add
> four "highway=footway"s to them). Cycleways are usually between the
> sidewalk and the road, so it becomes quite odd that a sidewalk is just
> a tag, but a cycleway is its own highway.
>
> * Here's the big argument: There's no information lost by adding tags to
> the road like "cycleway=track" (we need a few more tags though for the
> more exotic cases, like when the cycle track also serves as sidewalk),
> compared to adding separate ways. So I'd like to keep the simplest way
> then.

And you need tags for when the cycleway on the left is bi-directional, but on 
the right it's one-way. Or tags for when there is a cycleway only on one 
side. I suppose you want this to be done with tags/values like left_track or 
left:track etc. Which becomes a mess when somebody reverses the direction of 
the way without changing all the tags. Not to mention special turn 
restrictions for bicycles only, if you can't turn left with your bicycle, but 
you can with your car. etc., etc., etc.,

Yes real easy.

> * It's just a lot harder to make them their own highways. it's much
> easier to make mistakes.

Since it is impossible to make all the special cases above visible at a glance 
in an editor the opposite is true.

> * Rendering engines could handle it much easier if it were just a
> cycleway=* tag added to the road.

Please show me the simple rendering algorithm for mapnik and osmarender you 
have envisioned to make this working for all the special cases above. Until 
you do, I keep believing the opposite is true, since it is fairly obvious 
from the existence of Andy's cyclemap and the experimental Dutch cyclemap 
that they have absolutely no problem rendering cycleways that are drawn as 
separate ways.

> * You can usually arbitrarily go from the cycleway to the main road (to
> cross it for example).

Where I live there are numerous places where this is not the case.

> Routing applications could make use of that, if 
> it's just a cycleway=* tag. Maybe you have to watch out for parked cars
> for example, but I've seen cycle lanes where there are parked cars
> between you and the road as well, yet the cycle lane is a lane and not
> a track. (and before someone mentiones it: yes, relations like the
> dual_carriage relation could solve that, but let us first get relation
> support in editors a bit better before trying to put more and more into
> relations)
>
> * Routing hell, like mentioned above: adding cycle routes to an
> intersection with highway=cycleway next to highway=whatever will make a
> simple route crossing the intersection a patch of a dozen ways
> belonging to the route. Also for simple roads which aren't dual
> carriage, you're then forced to add two ways (one in each direction)
> instead of just the main road to the route relation.
>
> I've tagged the cycleways as their own highway once, but just doing that
> I got quickly convinced that doing that was just a bad idea, so I
> stopped and even just reverted everything to cycleway=* tags. So far I
> haven't heard one argument which invalidates the issues above enough
> that it convinced me highway=cycleway for these is a good idea.

-- 
m.v.g.,
Cartinus