On 29 September 2013 10:05, Colin Smale colin.sm...@xs4all.nl wrote:
**
Peter,
I say this because the '70 mph' value for maxspeed can only be used case
where a road is a dual-carriageway.
What about link roads and slip roads? Sometimes they seem to go on for
miles without an obvious other carriageway. Yet the correct maxspeed is
often 70mph, is it not?
How about saying that 70mph can only be valid on a way tagged as one-way?
In a word, I believe the answer is 'no'. I say that because the legal
definition of a dual-carriageway appears to be vague, with unclear
edge-cases. There are certainly examples of one-way national speed limit
trunk and primary roads which are not 70 mph. Possibly it would be best to
discuss some actual situations.
How about Junction 31 on the A14 junction to the west of Cambridge. Most
slip roads are currently 60 mph, but one is 70 mph. A short section of
parallel ways of the Huntingdon Road is shown as 70 mph however I am not
now clear if that short section constitutes a dual carriageway.
http://www.itoworld.com/map/124?lon=0.07067lat=52.23321zoom=15fullscreen=true
How about the many short sections of 'dual-carriagway' on the A120 in Essex
such as this one. Dual carriageway or not? I am not clear.
http://www.itoworld.com/map/124?lon=1.21929lat=51.92823zoom=17fullscreen=true
Or this junction between the M1 and A421. Again, short sections of
'dual-cariageway' and slip roads to both a motorway and a trunk road. What
is their status?
http://www.itoworld.com/map/124?lon=-0.60951lat=52.02764zoom=16fullscreen=true
It is for these reasons that I advocate setting maxspeed:type simply to
'GB:national' and then interpretting it to the best of our current
knowledge as a numeric limit in maxspeed. Possibly we should err on the
side of caution with the numeric limit.
Regards,
Peter
Colin
On 2013-09-29 10:14, Peter Miller wrote:
To attempt to summarise the situation:
- The maximum legal speed for any vehicle should be a number in
maxspeed following by mph.
- There should also be information available to say if this speed is
defined as a number in a circle or a black and white sign
- There is also benefit, for various reasons, to know if a road is
single carriageway or dual carriageway.
- There also seems to be agreement (in the form of silence from some)
that there is no clear definition of what is and is not a dual-carriageway
in the UK without going to court!
- OSM tagging policy is generally that one should tag what one sees.
As such, it seems unreasonable to ask a new mapper to great a situation
requiring a court case for every ambiguous section of road in the country
to establish if they are dual carriageways or single carriageways. This is
why I suggest we use GB:national to indicate that the speed is set by a
black/white sign.
We could however compromise and suggest 'GB:nsl_dual' where we know if is
a dual carriageway, 'GB:nsl:single' where we know it isn't and GB:national
where we aren't sure.
Alternatively, we could always use 'GB:national' for the maxspeed type and
add other tagging to indicate dual carriagewayness, either using
'carriagway=A/B' tag or a relation with type=dual-carriageway or similar.
Or.. and this is the simplest approach in the short term as far as I can
see which I have been advocating, we can imply dual-carriagewayness by a
combining a highway tag with the tag pairs 'maxspeed=70' and
'maxspeed:type=GB:national'. I say this because the '70 mph' value for
maxspeed can only be used case where a road is a dual-carriageway. As we
get clearer about what constitutes a dual-carriageway or not we then only
need to change with speed between 70 mph to 60 mph. We can then also
populate approach dual-carriageway tagging on these roads.
Regards,
Peter
On 29 September 2013 00:45, Nick Allen nick.allen...@gmail.com wrote:
Peter,
After your first post on this, my initial thought was that you were
correct and the simpler tag you were proposing was enough. I started
following your proposal, but I've thought a little more feel that the
more involved 'GB:nsl_single' type tag is actually needed I'll be going
back through my work over the last couple of days and changing it back.
My thinking is;
i/. The basis of GB law is that it is up to the individual to know what
the law states, and to comply with it. No matter what your SatNav tells you
it won't help you when you are standing in a court explaining your actions
- the SatNav is a guide only and some maintain that they are unsafe as they
distract the driver who may therefore miss the speed limits being displayed.
ii/. If you are driving a motor vehicle with very few exceptions you
should comply with the law regarding speed limits.
iia/. A built up area with street lighting (I'm not entirely sure how
you define built up area, and I seem to remember something about the street
lights being no more than 200
