[mkgmap-dev] Road speed through urban areas

Wed Jul 8 21:19:11 BST 2020

Hi Fernando & Greg

You need to use the maxspeedkph() or maxspeedmph() function to read the
OSM maxspeed tag as it understands values like "30 mph". Then,
following Greg's idea that you should use maxspeed:practical if set and
the that logic to compare speeds is going to be very tricky, just have
following near the start of inc/roadspeed:

maxspeed:advisory=* {set maxspeed='${maxspeed:advisory}'}
maxspeed:practial=* {set maxspeed='${maxspeed:practial}'}

It also needs something at the end to limit motorways for most
countries:

highway=motorway & mkgmap:road-speed-max!=* & mkgmap:country!=DEU
    {set mkgmap:road-speed-max=6}

Ticker

On Wed, 2020-07-08 at 10:57 -0400, Greg Troxel wrote:
> Fernando Trebien <fernando.trebien at gmail.com> writes:
> 
> > maxspeed:practical=* & maxspeed=* & maxspeed:practical < $maxspeed
> > {
> > set maxspeed='${maxspeed:practical}' }
> 
> Not really bearing on your particular problem, but I don't think
> checking with < makes sense. If maxspeed:practical is set, it
> represents
> the speed that people actually can reasonably drive.
> 
> It can be that this practical, socially acceptable speed is higher
> than
> the limit.  There is a road around me that is built almost like an
> interstate but has an inexplicable 45 mph speed limit.  Traffic
> normally
> flows at 70 mph.  Anyone going 45 mph is really in the way to the
> point
> of being dangerous, and people might call the police to report an
> impaired driver.
> 
> So if practical is higher, use it.  Which means "if practical is set,
> use it".
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