[OSM-talk] Cycle lanes

[Dave Stubbs]

On Mon, Mar 24, 2008 at 1:01 PM, Ben Laenen <benlaenen at gmail.com> 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
>   ||||

I count 8 ways?
Unless you are splitting all the ways at absolutely every intersection
which is probably a little excessive.

Obviously creating a way for every single cycle lane is going to just
cause a mess, so where they do just follow the road, on the road, it's
probably best to keep them as just a simple tag.
However, where they are clearly separate, it's probably best to tag
them as you would a dual-carriageway, and for the same reasons. With a
separate cycleway you generally can't just hop-on/hop-off without
being a menace to other traffic and there's sometimes even a physical
barrier; the way can also diverge from the main road way, taking
short-cuts round roundabouts or similar.

>
>  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.

That's just an argument for modeling the pavement properly. Most
pavements are just tacked onto the road as an extra "lane", but with a
kerb (to discourage the cars from using it :-) ), so I wouldn't
usually bother adding these as separate ways, but where the pavement
diverges or is clearly separate, it should probably be modelled as
such.

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

It's possible to argue that one both ways: it's easier to see what's
going on and where cycle tracks start and stop, and where exactly they
are.

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

>From practical experience I disagree.

>
>  * 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)

Potlatch is getting relation support sometime soon.... just awaiting
deployment :-)

Dave