[talk-au] maxspeed - best practice?

Michael James m.james at internode.on.net
Tue Aug 14 10:37:45 BST 2012


On 08/14/2012 03:30 PM, Ben Johnson wrote:
> In regards to residential areas - I remember last year there was some
> talk about the bot that added "50" with the (incorrect)
> "maxspeed:source" key = "default residential speed limit in Australia" 
> and I think there was consensus in the local community that this was a
> mistake.
> 
> With remapping some of my local areas, I'm now curious what's best
> practice in Australia is for tagging maxspeed on residential streets.
> Specifically...
> 
> a) is it even necessary or desirable to explicitly define maxspeed for
> every residential way - or should we just presume any
> highway=residential is maxspeed=50, unless otherwise stated?

What are we singling out highway=residential?

This is where I want to enter the debate as the whole thinking before
was just wrong as far as what the legislation actually says and what the
map uses as tags for roads.

1. The law :-
25 Speed limit elsewhere
(1) If a speed limit sign does not apply to a length of road and the
length of road is not in a speed limited area, school zone or shared
zone, the speed limit applying to a driver for the length of road is the
default speed limit.
(2) The default speed limit applying to a driver for a length of
road is—
(a) for a road in a built-up area—50km/h; or
(b) for a road that is not in a built-up area—100km/h.

Dictionary entry :-
built-up area, in relation to a length of road, means an area in
which either of the following is present for a distance of at
least 500m or, if the length of road is shorter than 500m, for
the whole road—
(a) buildings, not over 100m apart, on land next to the road;
(b) street lights not over 100m apart.

Note that there is no mention of the word residential in the law

2. Guidelines for highway=residential and highway=unclassified
The guidelines http://wiki.openstreetmap.org/wiki/Key:highway
give the direction that if houses are on the side of a minor road then
it should be tagged residential however on the edges of towns and cities
you can have such streets as per OSM's definition but they will fail to
fulfill the definition as given in Australian law for an Urban Road and
thus not have a default of 50kph

So when should it be tagged ?

In my opinion you should only tag ways that are either signed posted and
you tag it with the figure given and appropriate source ref

Alternatively if you have observed that a street satisfies the
definition given in the road rules for the default to apply then tag it
as such and give the source as built_up_area

tag if signed
maxspeedsource=sign

tag if not signed and satisfies the definition
maxspeedsource=built_up_area



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