[Tagging] Intermittently unprotected cycle track

[Richard Fairhurst]

Hi all,

Let me introduce you to one of London's better cycleways:

https://www.openstreetmap.org/#map=19/51.53397/-0.00715
https://cycle.travel/map?lat=51.5254&lon=-0.0335&zoom=17

You might look at this and think "that doesn't look like 'better' to me, 
it's full of 45-degree bends". And based on OSM you would of course be 
right.

In reality it isn't full of 45-degree bends. It's a continuous straight 
route. But although it's mostly protected (i.e. concrete barrier 
separating it from the car lanes), the protection gives out at junctions 
and crossings, so turning traffic can cross. Here's an example 
(apologies for Google link):

https://goo.gl/maps/rFHNHdCxMCp

Currently, it's mapped in OSM as a highway=cycleway for the segregated 
bits, and then it rejoins the highway=primary road (with cycleway=lane) 
where the barrier gives out.

This is correctish in terms of tagging but not in terms of geometry. The 
current mapping implies 45-degree turns which the cyclist doesn't have 
to take - they just continue straight on. Breaking geometry to enable 
tagging is bad in itself, misleading on renderings, and unsurprisingly 
confuses the heck out of routers.

How should we represent this?

My gut feeling is that it would be better to map it as a continuous 
highway=cycleway but with 'protected=no' for the bits where the concrete 
divider isn't there.

Another alternative might include deleting the cycleway completely and 
just using cycleway=track on the car road, but this seems suboptimal as 
you can't then easily apply tagging that applies distinctly to the 
cycleway (surface, route relation membership, etc.) without lots of 
namespacing.

Or we could just go with highway=cycleway and no additional tagging, on 
the basis that 'unprotected' is implied by the pedestrian-crossing tags 
and the junction geometry - i.e. obviously there's no protection there 
because we have a junction which cars can turn across.

Any preferences?

cheers
Richard