[Talk-GB] National speed limit changes

Sun Sep 29 09:05:16 UTC 2013

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? 

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.54 at 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 yards apart) will have a speed limit of 30 mph unless there are signs indicating otherwise, & there should be repeater signs at intervals if it is not a 30mph area.
> iib/. National speed limit signs - the national speed limit has changed during my lifetime. Motorways are fairly simple, and for a car (not towing) it will be 70mph. Two-way roads with a national speed limit sign are also fairly simple, being 60mph for a car (not towing). Dual carriageways - little bit more complex - an island in the middle of the road to assist pedestrians to cross is not sufficient to make it a dual carriageway, but you would need to look at the current case law to help in deciding what exactly is a dual carriageway. I don't think a long length of wide road with the lanes divided by white crosshatch markings on the road, even if this exists for a length measured in miles, counts as a dual carriageway - it needs to have a physical barrier involved.
> iiic/. A prescribed limit indicated by signs such as '40', '50' etc..
> 
> iii/. The current software writers who seem to be using OSM data are mainly wrestling with the basics of navigating a car anywhere in the world but I think steps are being made towards navigation for larger vehicles, and these vehicles are likely to have different speed limits imposed on them in GB national speed limit areas. If they are writing software for navigating a 40 tonne lorry across Europe then the least we can do is try to indicate what type of road it is so they can attempt to give an indication to the driver of what is the maximum speed they may legally travel at.
> 
> Regards
> 
> Nick
> (Tallguy) 
> 
> Hi Peter,
> 
> Thanks for replying here.
> 
> Peter Miller wrote:
> 
> So...on the basis that we should tag what is there, we see a white sign
> with a black diagonal line on it then that is what we should indicate. We
> do of course interpret that by putting what we believe if the correct legal
> speed limit in maxspeed. As such a single carriageway national limit is
> coded as "maxspeed:type=gb:national,maxspeed=60 mph". As dual carriageway
> is tagged as "maxspeed:type=gb:national,maxspeed=70 mph". The motorway
> version is "highway=motorway,maxspeed:type=gb:national,maxspeed=70 mph".
> 
> I understand the potential problem (does a national speed limit dual
> carriageway slip road count as a dual carriageway or not?) but am concerned
> that changing e.g. "GB:nsl_single" to "gb:national" will:
> 
> o potentially obscure any underlying data errors (imagine something tagged
> "maxspeed=70 mph, maxspeed:type=GB:nsl_single")
> 
> o make things more difficult for data consumers (if only by changing the
> data from something that they might be expecting)
> 
> o confuse new mappers who see data that they've entered being changed
> because it's "wrong", when in reality there really isn't a concensus on
> this.
> 
> I fully accept that national speed limit tagging in the UK is a mess (at
> the time of writing 4 of the top 6 values for
> http://taginfo.openstreetmap.org.uk/keys/maxspeed:type#values [1] could mean
> the same thing) but any consolidation must proceed following discussion.
> 
> Sure, and I am politely inviting people to discuss the subject now and am
> suggesting that it makes a lot of sense to consolidate around a tag value
> which describes what one sees in front of one on the ground, ie a black and
> white sign. To be clear I in the habit of using the nsl_single and nsl_dual
> format until PinkDuck politely pointed out that I was tagging some
> slip-road etc incorrectly and we agreed that is made more sense to avoid
> the confusion in the first place and use the simpler gb:national.
> 
> With regard to the other point:
> 
> For avoidance of doubt, all my edits have been fully manual.
> 
> I don't believe that anyone has suggested otherwise
> 
> I was responding to Roberts comment above that "I certainly don't think
> there has been any discussion of or agreement for a mass mechanical edit to
> change existing values."
> 
> although I have certainly suggested that you may not have visited all of
> the places that you have been changing the speed limit for. There is
> clearly a sliding scale between "I've surveyed an area, and everything that
> I've edited is based on the results of that survey, aided by e.g. Bing,
> OSSV, and other named sources" and "I've changed a bunch of tags worldwide
> based on who knows what information without even looking where I've changed
> them".
> 
> The wiki's "mechanical edit policy<http://wiki.openstreetmap.org/wiki/Mechanical_Edit_Policy [2]>" 
> 
> (as currently written) suggests that changes of this type may be covered
> ("search-and-replace operations using an editor... unless your changes are
> backed up by knowledge or survey") - I guess that it depends on what you
> mean by "knowledge" **.
> 
> Clearly no-one's going to object to some tag-changing edits
> (designation=public_fooptath to designation=public_footpath for example)
> but in this case there's enough doubt - other mappers have said "I think
> the changes should reverted" and "This tag is vital" in the replies to my
> original mail.
> 
> Based on that, where you've changed e.g. "GB:nsl_single" to "gb:national"
> would it be possible for you to revert your changes? There's clearly a
> discussion to be had going forward about which one of GB:blah, UK:blah,
> gb:blah and uk:blah we need to keep, but based on the replies so far there
> doesn't appear to be a concensus to support merging of everything into
> "gb:national".
> 
> I don't hear a clamoring for such a reversion, and indeed I don't think
> anyone in OSM is sufficiently knowledgeable able the law to say for sure
> which tag should be used in all cases as I have indicated above.
> 
> Peter
> 
> Cheers, 
> Andy
> 
> ** In which case quite possibly mea culpa for the changesets that I refer to here<https://lists.openstreetmap.org/pipermail/talk-gb/2013-September/015227.html [3]>- it's not black and white. 
> 
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Links:
------
[1] http://taginfo.openstreetmap.org.uk/keys/maxspeed:type#values
[2] http://wiki.openstreetmap.org/wiki/Mechanical_Edit_Policy
[3]
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