[mkgmap-dev] Possible maxspeed patch

Thu Aug 27 08:42:34 BST 2009

Marco Certelli wrote:
> Hello,
> 
> as I said some months ago, deciding the right speed to set in the garmin map for each way shoud be a new mkgmap function.
> 
> The function should take into consideration:
> 
> the assigned OSM highway tag
> the assigned OSM maxspeed
> the number of crosses per km (maybe the number of routing nodes / lenght)
> the number of traffic_lights per km
> the curves ((for each node, add the angle) / lenght))
> ....
> 
> All these info shoud be properly combined to tell how fast a vehicle can run on that road. We should experiment a lot...
> 
> But maybe this is too far away ;-)
> 
> Ciao, Marco.
I agree with this. We have a level crossing near us where the barriers 
are down for around 2-3 minutes and are down around 10 times an hour. At 
the moment routing always goes across the crossing rather than using an 
alternative route (which takes about 30 seconds longer but which would 
be quicker on average).

I do have doubts how it work in practice. In practice the average speed 
of a road comes from a mix of fast sections (ie. plain road) and slow 
sections (junctions, lights...). Whilst we can count crossings/traffic 
lights along a road and get the overall speed for the road right, it 
doesn't work so well if you turn on/off along the road.

This patch allows you to switch the methods used to set the road speed 
in the IMG file. At the moment it simply switches between maxpseed and 
the style file setting. However, it would be easier to include an extra 
option (eg. "MarcosMethod") to offer extra options if somebody wants to 
write it.  Maybe it would be better to change the option in the patch 
from "maxspeed" to "speed".