[OSM-dev] Gosmore preferring unsealed tertiary route

Lambertus osm at na1400.info
Mon Aug 10 14:14:31 BST 2009


John Smith wrote:
> --- On Mon, 10/8/09, Lambertus <osm at na1400.info> wrote:
> 
>> Really, I'm no traveling salesman, but I lean towards
>> defining routing classes for all the highway=* tags and add
>> children to each of them for different situations (like
>> surfaces, width, turns that cross the other lane, traffic
>> lights etc) that add or subtract average speed or add
>> penalty time (average speed penalties have no use on nodes
>> like bollards or traffic calming).
> 
> You could do this based on estimated m/s, a motorway at over 100km/hr is a minimum of 28m/s, obviously if maxspeed is available that could nail it down much better.
> 
That's indeed how Gosmore works, the routing rules specify what the 
average speed of a certain road is (usually a few km lower than the 
maxspeed).

> Lots of unsurfaced roads are maxspeed=100 but you wouldn't be able to sustain that all the time, I'd say a 30% hit at a guesstimate.
> 
Legal speeds and practical speeds are usually not in relation with each 
other when talking about the unsurfaced roads. On the other hand, I've 
driven some South African 'washboard' dirt roads with a rental car and 
could not sustain more then 40km/h while the windows were shaken loose 
in their hinges. But the typical 4WD 'bakkies' pickups roared past us at 
full speed.... So average speed is difficult to determine for such roads 
unless you differentiate between 4WD and luxury cars.

> calming devices drop you to 15km/hr or there abouts.
> 
Yes, but as they are often represented as a node in OSM, giving them an 
average speed is meaninless. A time or point penalty seems more suitable.





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