[Tagging] Conditional restrictions accepted - turn restrictions ahead?

Rob Nickerson rob.j.nickerson at gmail.com
Tue Oct 16 20:42:56 GMT 2012

I'm still not convinced that you need to introduce a new tag (be that
"applies" or "condition").

1. Although it is difficult to calculate how many turn restrictions have
some form of "condition", the numbers can't be that many in comparison to
normal restrictions that apply at all times. Adding the condition data to
the "restriction=*" tag therefore will not break the majority of
restrictions (they stay unchanged). Similarly adding the information in a
new tag will not break the majority of restrictions.
2. For those restrictions that do have conditional details, if:
  a) you add the details in "restriction = " you break the current tagging
and routing software will not know how to interpret it. The routing then
does not include the turn restriction (i.e. no restriction when you want
one), or if
  b) you add the condition to a new tag then the routing software does not
see it (i.e. you have a restriction when you don't want one).
Both cases need the routing software to be updated...
3. ...and that is exactly what a Request For Change (RFC) is for. It is as
the name suggests a communication with your users : "Hey guys, we want to
change this to make it better. What do you think? Great, can you update
your systems so that you are ready for the new tags"

As you see all proposed ideas will need the end users to change something.
And, in fact, as we currently don't have a way of including conditions, we
may already have incorrect turn restriction in OSM.

_Conclusion_: Whatever we do should keep the tagging as simple and easy to
understand as possible. As we already have some "applies" type information
in "restriction:hgv = no-u_turn", my gut instinct is to include all the
"applies" type info in this tag. Hence the example "*restriction:hgv =
no_u_turn @ (length > 6)*".


p.s. Any change to day on, day off, hour on, hour off, will also break the
existing scheme (but is in my opinion worthwhile).
p.p.s. All my previous examples are fictional. More real world photos fully
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