I take exception to the comment that “there will be too many exceptions to the 

In the country I live in each state has a set of “prima facia” speed limits for 
various types of roads. Those are basically default speed limits to be enforced 
unless otherwise posted by sign. Virtually no residential road in my state has 
a speed limit sign but if you exceed 25 MPH you can be ticketed for speeding. 
Rural highways are signed only at infrequent intervals, but exceeding 55 MPH 
can result in a ticket.

A) We should only tag what is on the ground verifiable. By that rule we should 
not currently tag these “prima facia” speed limits (no speed limit sign to 
verify a maxspeed tag value).

B) A routing app currently has no way to determine a default speed (one to be 
used if no maxspeed=* tag found on way). These can vary by jurisdiction and I 
can imagine situations where a national default is overridden by a state 
default and/or local municipality default. Should all routing apps go to a 
different geographical database to get defaults? If so, why not go to that 
other database for everything and ignore OSM?

It make perfect sense to me to allow administrative areas to be tagged with 
default values for otherwise untagged items within the jurisdiction. If 
something deviates from the default, as in your “speed limits varies depending 
on local topography”, then it will be signed and we should tag per the sign. 
But many, many roads in my area are not signed and yet have legally set maximum 

At present, I usually ignore the local verifiability constraint and simply put 
a maxspeed value on residential roads after I’ve surveyed them even if they are 
not signed. If I am feeling a bit more energetic than usual I may also add a 
source:maxspeed with a value citing my state’s motor vehicle code. It would be 
a lot easier if I could rely on a default value set on my state’s 
administrative boundary.

> On Sep 1, 2017, at 9:25 AM, Dave F <davefoxfa...@btinternet.com> wrote:
> Hi André
> Assuming or defining a default should be based on the number of different 
> values within the set. 
> For the examples you give:
> maxspeed shouldn't have a default. Apart from on motorway classed roads, 
> speed limits varies depending on local topography. There will be too many 
> exceptions to the rule.
> driving_side is defined nationally so has a default. (I'm sure now someone 
> will now provide examples where that's not the case).  Any router worth its 
> salt, should be able to check which country it is in.
> DaveF 
> On 31/08/2017 12:49, André Pirard wrote:
>> Hi,
>> Examples: either each road is tagged with maxspeed=* 
>> <https://wiki.openstreetmap.org/wiki/Key:maxspeed> speed limit and 
>> driving_side=* <https://wiki.openstreetmap.org/wiki/Key:driving_side> or 
>> there are defaults.
>> I'm reviving this remark because the examples are numerous:
>> The Belgian Flemish community wants to tag maxspeed=* 
>> <https://wiki.openstreetmap.org/wiki/Key:maxspeed> on every road instead of 
>> using a default. Is this a new specification and where is it written? Must 
>> that now be done in every country?
>> The current language= proposition wants to do it without defining defaults. 
>> Really? language= on every name= ?
>> Other examples are maxheight in tunnels. Osmose just accused me of someone 
>> else's omitting maxheight. It shouldn't be necessary if it's the default, 
>> that is if there is no sign for it, but Osmose likes to yell just in case.
>> countless etc.
>> Please choose.
>> Either the defaults are in the OSM database and it takes just a routinely 
>> map fetch to get them all updated timely,
>> or each other router (GPS) writer implements them each their own way from 
>> various random other files. It's not well clear how contributors ca update 
>> all those files instead of OSM and it typically needs a full software update 
>> for each little default change, depending on writer's availability.
>> Please choose.
>> There is a Proposed_features/Defaults 
>> <https://wiki.openstreetmap.org/wiki/Proposed_features/Defaults> that puts 
>> the defaults in OSM and it's an EXTREMELY HUGE mistake to have marked such a 
>> paramount good work as abandoned because nobody continued the work.  For the 
>> sake of OSM, especially routing, please reopen it.
>> I don't claim that it is the good solution but I do claim we should work on 
>> such a default database in priority.
>> I didn't analyze it in full depth, but I have the following remarks:
>> - Why not allow the def keyword in the border relation itself? But it could 
>> be called zzdef to cluster at the key end.
>> - If a separate relation is preferred, it should be pointed at by a 
>> "defaults" role in the corresponding border or other relations so that it 
>> can be found.
>> - to ease scanning a border tree upwards, a "parent" relation should exist 
>> in border relations.
>> In hope of a well structured OSM,
>> Cheers 
>> André.
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