[Talk-us] Route Tagging Consensus

Richard Weait richard at weait.com
Sat Oct 30 04:57:26 BST 2010

It feels like we have been going around in circles on this for almost
two years.  I wrote this in March 2009.


Can we reset just a bit?  Rather than jumping to an answer "The tags
shall be this!" can we look at what our ideal goals would be?  So from
a superficial viewpoint, I want highway shields to be "right", and
perhaps even to be "cool".  But what else?

Looking at the history of shields in OSM, I think Lars did Interstate
shields first in TopOSM, where he appears to use the same size shields
for 2-digit and 3-digit Interstates.[1]

I don't recall anything else having shields until the MapQuest style.
They appear to use both the 2-digit and the wider 3-digit Interstate
shields. This is a nice improvement.

The cartographers that made these shields work at all are to be congratulated.

Goals. My goals for shields are the following.  I'd like your help too.

0) Don't break the database with my ego.  I can be right or wrong or
somewhere in between, but I won't apply mass changes to the DB as part
of my argument.  Whatever is decided, local mappers can "fix it" by
adjusting to the consensus solution over time.

1) Fall back to the default OSM "lozenge" shields.  If tagging is
incorrect or incomplete try to do something sensible without breaking
existing renderers that might not understand real shield rendering.
For instance, the main osm style is unlikely to adopt shields. I can
accept that.  Let's not break what they currently do with the

2) Make it easy on mappers.  They are the ones doing the work.  Let's
keep this as simple as possible, but no simpler.  ;-)

3) Make it inclusive and extensible. The US isn't the only place with
highway shields.  Once we get this right, others will want to play as

4) Once we have simple shields working for everybody, wouldn't nice
multiple-shield rendering be awesome?

Suggestions. And I have some suggestions.  Again, your suggestions are
welcome too!

First, we should call this one "undecided" for now.  We've been going
back and forth for a week (and two years) and we still aren't
universally thrilled with any of the proposed solutions.  No problem.
We don't have to solve it today.

Second, we should resist the temptation to make further suggestions
without a working example to go with it.  Yes, that will reduce the
number of participants in the discussion.  No, that isn't fair.  But
perhaps the current discussion could be better focused with a small
dose of, "and here is how I made it work." Yes, I know that tagging
for the renderer is bad. I'm not suggesting tagging for the renderer,
I'm suggesting "tag in some way that can demonstrably work."  ;-)

Can we just name the shield we see?  It would be mapping what's on the
ground.  It would be verifiable.  I don't mean name it to the point of
compulsive detail like, "2-digit Interstate Shield that is kind of
sun-bleached and has two bullet holes (lower-right) and a bit of rust
on the left."

I'm not suggesting that we describe every highway sign.  "30-ft wide
blue sign with white reflective text, 'Huntington State Park \n Next
Exit'" just seems too much.  But at some level of abstraction, to get
shields right, are we not just describing the shield?

Oh, and here is an improvement over the brutal hack I put in the old
article. This DB is not getting minutely updates.


[1] Lars has US Route shields and MA, rectangular MA state road
shields as well.  Nice work.  I'm a huge fan of TopOSM.  Go see it if
you haven't had a look before.

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