[OSM-talk] Motorways and Motorway_link

Dermot McNally dermotm at gmail.com
Sat Oct 4 15:33:43 BST 2008


2008/10/3 Lester Caine <lester at lsces.co.uk>:

> My comment about the speed limit was that the 60 applies ( or even less if a
> local limit applies on the approaching roads! ) UP TO the start of motorway
> sign and some of these link roads that is simply not at the 'start' of the
> road. At some point, if correct speed indication is to be provided for route
> planning, then the position of the actual start point is as important as
> placing a change of speed limit at the correct point?

Are we not splitting hairs here? Certainly, the instruction to a
learner driver is that the chopsticks sign indicates the start of
motorway regulations, including any implied speed limit. Likewise, the
standard signing practice is to place these signs at the commencement
of any road that leads inescapably to the motorway. Our tagging
practice is to reflect this "motorway zone" through use of the
motorway or motorway_link tags.

So far so good. If I'm reading you right, you're describing situations
where the chopsticks sign appears some distance past the point of last
escape. That happens from time to time, and is simply a case of the
sign being wrongly placed. This is particularly common in Ireland,
where there's huge variation in the placement of the sign, including
some recent cases where the sign has been practically at the merge
point with the mainline.

My personal practice is to ignore the implication of badly placed
signs and apply a motorway or motorway_link tag from the point of last
escape. This provides the most useful view of the on-the-ground facts
and should also reflect the underlying legislation for the road.

Dermot

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