[OSM-talk] Cycle lanes

[Ben Laenen]

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.

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

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

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

Greetings
Ben