I’ve brought this up many times before in other places, but I’m gunna do so again, becuase It rather frustrating having to use the data within the restrictions of the tags, rather than for anything you wish. It’s trunk roads.
It still seems impossible to render a map of the UK trunk road system. I don’t mean a map of all roads with blue or green signs, but the trunk road system as shown, here, here, here and here…etc…,etc….
Grouping roads by signage is all ok, but we also need to tag them so we can filter off half the roads and produce an uncluttered map. Having way too many features appearing in a small space makes a map almost unusable in most cases. Try using this for quickly finding where you are and where you have to go for example. It’s considerably worse than an OSM example, but OSM’s low zooms are still unesseserly cluttered, and there not particularly practical. I have a feeling Google had an influence on this, rather than much discussion.
I still see it as strange, that we tag primary roads as trunk based on signage, as a google search for ‘UK trunk roads’ will show the Motorways and HA managed highways, but I guess it’s just one of many of OSM’s oddities. It’s also contradictory to Wikipedia which says “Trunk roads in England are managed by the Highways Agency”. What really matters though is ‘not being able to make a map’. We can be odd but lets not be restrictive. Can we please either have an additional tag for the real trunk road network, or just tag maintenance=highways agency where applicable. (This is assuming that these map examples are only showing HA managed roads??)
There was a wiki page somewhere, which I am failing to find, which lists some basic principles of map rendering. There are a few points I recall that are being forgotten about here and on other matters, but I think a rule I go by, that applies here, is that when ever something is mapped so commonly that it clutters, tag more specifically.
Also the ‘tagging based on signage’ arguement somewhat falls apart for various lower status highway keys, but that can be saved for another day!