Re: [OSM-talk] routing over bollards mapped as linear ways

2019-10-13 Thread Martin Koppenhoefer 


sent from a phone

> On 13. Oct 2019, at 21:44, Tom Pfeifer  wrote:
> 
> - should we required extra tagging of the shared node, or abolish such way 
> barriers?


there are also barriers that are rarely represented as nodes, like guard rails, 
fences, walls, retaining walls, chains, etc. so checking for barrier ways would 
probably be required for good routing on OpenStreetMap data (even if 
experienced mappers often not presume that routers evaluate them, hence they 
add additional information on the crossing node, ideally it should not be 
necessary).

Ciao Martin 
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[OSM-talk] routing over bollards mapped as linear ways

2019-10-13 Thread Tom Pfeifer 

The wiki allows barrier=bollard on a way. It demands however:
"If rows of bollards are laid across highways, make sure they share nodes with what they block since 
routing happens at the edges of area highways at present."


Indeed bollard is used 331k on nodes and 12k on ways.

While the wiki statement above has a focus on areas, the situation is already complicated for a 
router calculating on a linear way.


Assume we have a road that is blocked with several bollards across, which are mapped as a way, 
sharing a node with the highway. This sharing node is currently untagged.


A router would normally evaluate its routing graph for specific nodes on it, not necessarily 
evaluate any way that crosses it. Thus it finds barriers as a node, or traffic lights.


To consider the barrier-way just sharing a node, the router would need to evaluate each and every 
way it intersects for a barrier tag, which is a high extra load. We had a similar discussion a while 
ago when a user proposed to join two roads entering and exiting a roundabout in the same node.


Thus my questions;

- which routers currently evaluate way-barriers across a road based on an 
untagged shared node?
- should we required extra tagging of the shared node, or abolish such way 
barriers?

For bollards, it might be easy to map them individually, having one squatting 
on the road way.
For other barrier types, such as gates, this might be trickier.

cheers
Tom

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