user_5589 (2020-10-24 11:34:03+00:00): The use of those tags is deliberate. I actually consider the current way of dealing with many aspects of the traffic signs to be inadequate.

It's entirely possible to have traffic signs tagged on different objects, so tagging has to be able to accommodate those. Like I have they can be tagged in the ways they affect, at the point where the effect starts. They can also be tagged where the signs physically are on a dedicated pole or attached to a streetlight or a wall. Multiple signs can also be at the same point. In the Prospect Road case it's the start and end of the 7.5 tonne weight limit which coincide, as well as signs for the cycle tracks beside the road. In those cases it's just two signs, but it can be three or even four if there are two signs in each direction (say). It might even be conceivable to have one of these weight limits but have a weak bridge within said weight limit where only 3.5 tonne vehicles can pass over. Using the namespace for each sign clearly assigns tags to that particular sign. With the namespaces it would be unambiguous which sign refers to the 3.5 tonne limit over the weak bridge and which sign refers to the 7.5 tonne general town centre limit. It's also important to note that this tagging allows distinguishing between the sign telling you about the limit 1 mile ahead and the actual limit itself.

This approach also is capturing what the sign says, not the portion of the way where the effect is actually in place. It tries to capture a lot more of what the sign says rather than just the existence of the sign. Hence nearby on Brunswick Street you will see tagging of sign 557.1 which is warning of speed bumps ahead. However that sign occurs at the end of several hundred yards of a sequence of speed bumps. What is the point of it then? It is warning of speed bumps ahead on two of the exits from a junction. The tagging of traffic_sign=GB:557.1 captures the specific sign used, the tagging of traffic sign:direction=forward gives the sign facing, the tagging of traffic_sign:arrow=left|right indicates that there are two different sets of speed bumps being warned about down roads off to the left and right of the current road and the tagging of traffic_sign:distance=700 yards|450 yards indicates unambiguously what lengths of the road off to the right and the road off to the left are being warned about. That tagging methodology was borrowed from the turning lanes tagging scheme.

The aim is to capture more semantic information about what is on the sign than just that it's a sign warning about speed bumps ahead. Use of the namespace allows this to be done unambiguously and using the namespace all the time, even when maybe not strictly necessary, makes parsing the information easier and accommodates the use of different tags on the same node. So this would allow tagging of multiple signs attached to a street light pole separately showing the facing of each sign, and the facing of the streetlight and information shown on each sign.

Use of this schema even allows the capturing of distinct, unambiguous information about two instances of the same sign on the same pole but facing in different directions and distinguished otherwise only by the information on supplemental plates below those signs. See the instance of sign 642 (a clearway) near the junction of the A452 and the unclassified road coming out of Bishops Tachbrook. It's sign 642 in both directions but one way gives warning that a clearway exists in both directions at the junction up ahead and the other ends the clearway on the side road after turning into the side road.

I've started tagging traffic signs this way to give what I've been thinking of a good test run and to show that it works in the real world of tagging. I'm thinking of bringing this up on the tagging mailing list and and also posting about it on the wiki as a tagging proposal.