The subject of UK speed limits and problems of mapping them has come up a couple of times on these lists.
Firstly we have a problem because many users want a single numerical value in the maxspeed tag, despite UK legislation having a range of speed limits for road dependent on the physical nature of the road. Secondly our Speed Limit legislation is an utter mess, with poor simplified guidance that confuses people. I suppose you can argue that our problems with tagging speed limits is appropriate because it mirrors the mess that is our speed limit legislation. Last year, when I was a bit more active in OSM, I wrote up all my notes on Speed Limits on my OSM wiki page. https://wiki.openstreetmap.org/wiki/User:Jamicu/UK_Speed_Limits Worth reading because a few posts before show some people are making perfectly understandable but incorrect conclusions about speed limits eg 1 On 21 September 2013 22:09, Andy Street <[email protected]> wrote: > I'm also not a huge > fan of the current practice of placing "single" or "dual" in the > maxspeed:type tag either as I consider the number of carriageways to be > feature of the road rather than the speed limit. > > Regards, > > Andy Street > Single or Dual refer to two of our three national speed limit types. NSL speed limits are created by the physical nature of the road and *not*signs. Dual & Single are definitely a "feature" of the speed limit. eg 2 On 23 September 2013 09:34, Philip Barnes <[email protected]> wrote: > National speed limits rarely apply in built up areas, other than > sometimes on faster feeder roads. The built up area limit in the UK is > 30mph, unless signposted differently. This is implied by the presence of > street lighting. 30mph limits, where there are no streetlights, require > repeater signs. > > Phil (trigpoint} > National speed limits nearly always apply in built up areas. The 30mph 'built up area limit' you refer to is the third type of NSL, the NSL Restricted road type. Along side the other two NSL's it is created by the physical nature of the road and *not* signs. But getting to the main point, the use of maxspeed:type=national I strongly disagree with removing data which tells us the type of speed limit and replacing it with a word that implies 1 of 3 types of speed limit is in place. It's useful information and more importantly it's the correct information. I'm not sure if this is actually the case here though? Peter, you argue that your mapping what's on the sign? But the signs do not create the speed limit for a NSL road, its the physical features of the road that create the NSL type. That means '*System of Street Lighting*', '*oncoming traffic separated by barrier*', but if neither of the previous applies the road is 'single carriageway NSL' Personally, I think having two tags is bad practice, and that we should remove the numerical value from the maxspeed tag and replace it with the correct speed limit type. End users should then use a table to get the speed limit for the vehicle they're interested in. I accept its a complex subject and I accept average users of OSM will find it easier to simply type in the maxspeed for cars, but the more confident users of OSM should be seeking to improve data, and not strip it out. Having access to NSL types is very useful especially when we hear about plans to change speed limits. Jason
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