Felix Hartmann <extremecarver@googlemail.com> writes:

On 30.04.2010 15:22, Greg Troxel wrote:

...

so we really need a tag for typical_speed, because you're saying that speed limits and typical speeds are not all that well correlated. This is not really about mkgmap.

Well of course. What I'm saying is that taking maxspeed to set the road_speed in mkgmap, makes no sense at all. Actually typical speed is not needed, because a clever style-file can guestimate the typical speed very well (except rush hour and night). I think the maxspeed treatment is important, but it has to depend on the type of road. Knowing maxspeed is 80km/h or higher, enables us to be certain we look at a highway outside of a city-limit, which of course will have higher typical speed than a highway inside city limits - so maxspeed is very important in assesing the map data. However it is useless for using to directly set the road_speed (in NT maps, Garmin is using a seperate maxspeed, while the road_speed is supposed to keep care of typical speed).

All of that has region-dependent knowledge about the relationships between road types, legal maxspeeds and the typical speeds. It's quite clear that your world and my world are very different and that your rules won't work in my world - in the US a road posted at 50 mph can reasonably safely be assumed to be travelable at 55 mph unless congested due to being in a city. That's all fine, but I think argues that we really need typical travel speeds in the database.