[Tagging] access restrictions on ways

[André Pirard]

On 2012-09-17 16:57,  David ``Smith'' wrote :
> Excuse me if I don't understand the situation entirely, but I think 
> the problem is the actual access restriction or enforcement of it is 
> different from a literal reading of the signs.  This must be the case 
> if the signs don't give adequate information to completely describe 
> the restriction. In that case, do your best to determine the actual 
> restriction as it is enforced and map accordingly.
I gave extra info showing that this sign is more a fight shield that a 
road sign.
But OSM must not inform readers of what road signs should be but of what 
they are.
In everybody's mind, access restrictions is to an area because it 
reflects the places they can't reach.
But the legal terms say that C23 is a signal you can't pass, one way, 
that's all.
That's a node sign.
> Access restriction tags on nodes should work fine for routers, but 
> remember if the node is an intersection, the access tags apply to all 
> movement through the intersection, and you probably want to avoid 
> that.  Also, such restrictions are less commonly visible on rendered 
> maps; for this reason I prefer to put access tags on ways if reality 
> can be accurately modelled that way.
> On the other hand, if the restriction exists at a point not at an 
> intersection and only for one direction of travel, I would have to 
> split the way there and make a no_straight_on turn restriction 
> relation with except= or for= tagging to indicate what vehicles are or 
> are not prohibited.
> Also, if a road does not permit passage of vehicles unless it's the 
> only choice (such as going to or from that road or a side street with 
> no other outlet) then remember access=destination (or hgv=destination, 
> or whatever else might apply) is something we can do.
And if you want to make it a way restriction, that's up to the point 
where other users could not see the signal.  Over 50m in this example !!!

André.


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