[OSM-newbies] postcodes, housenames, speed limits

[Dermot McNally]

2008/4/24 Andy Robinson (blackadder) <blackadderajr at googlemail.com>:

>  I was expecting someone to point this out. My take is that the root tag is
>  the the highway and it has a number of lanes, not all of them necessarily
>  used. For instance, the M42 around Birmingham now has hard shoulder running
>  at certain times. So lanes=4 is right.

No - lanes=4 is right during those times that the shoulder is
designated a running lane. These dynamic systems represent a problem
for us in any case, since we want the map to inform the driver of the
conditions, yet a simple lane count can't do that - he doesn't care
about the hard shoulder as a presumed 4th lane if he can't drive in
it.

So let's pretend it isn't the M42 (it usually isn't). Does the M6 also
have 4 lanes in your world? I'm cautious of the suggestion that
including the hard shoulder is valid as a means of allowing accurate
rendering of width. Partly because we have a width attribute, partly
because we are free to add a hard-shoulder one and partly because lane
widths differ across road types and countries.

>  having said all that I agree that knowing that only three lanes of a
>  motorway can be used is important too,

No, it isn't important "too", it's the reason we have a lanes
attribute (others should feel free to contradict me here). Knowing the
width is important "too", and we have an attribute that we can use for
it.

> so I would suggest this be another
>  tag, running_lanes=3.

Not required, if sufficient consensus exists that "lanes" is supposed
to refer to running lanes, which I'm guessing is the case.

> Its really only motorways where this issue crops up

Not so: Ireland, for instance, uses hard shoulders on most non-urban roads.

> (plus a few 3 lane roads where the central lane has been chevroned) so
>  having two tags for motorways and the few exceptions is probably no big
>  deal.

Maybe I'll be surprised, but I suspect that your usage of "lanes" is a
minority one. So if we need additional tags, it would be to record the
existence of hard shoulders or any other non-running part of the road
surface you consider interesting. But frankly, you'd be better off
using the width attribute.

Dermot

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