[Talk-GB] maxspeed changes

[Andrew M. Bishop]

SomeoneElse <lists at mail.atownsend.org.uk> writes:

> Andrew M. Bishop wrote:
>> As the author of an OSM data consumer (the router "Routino") I think
>> that distinguishing between single and dual carriageways is mostly
>> irrelevant in the argument for preferring numeric values for maxspeed
>> tags.  The real reason which I see, and which is much more difficult
>> to handle, is when you consider that there are ~200 countries in the
>> world and they each might have their own speed limits.
>
> How do you handle the routing of vehicles for whom the UK national
> single-carriageway speed limit is not 60mph?

At run-time a speed limit for each type of road can be specified (or a
default one picked from the pre-defined profiles for each mode of
transport).  When routing the lower of the road's "maxspeed" tag value
and the routing profile's speed limit for that road type is used.

You could say that this means that the maxspeed tag is useless in most
cases because if it isn't specified (or isn't parseable) then the
run-time limit specified for each road type gets used instead.  This
is true except that there is only one run-time limit specified and a
trans-national route needs to take account of local laws.  A limit
tagged on the highway is always better than a router's default.

At the moment though Routino doesn't store the value of "maxspeed:hgv"
tags but if people started using them then it might be worth adding.

Perhaps those hypothetical JOSM tagging presets that I suggested last
time should have the full set of limits included.

-- 
Andrew.
----------------------------------------------------------------------
Andrew M. Bishop                             amb at gedanken.demon.co.uk
                                              http://www.routino.org/