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johnnyzhangzhao / monav

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Routing prefers highway all the time #85

Open GoogleCodeExporter opened 8 years ago

GoogleCodeExporter commented 8 years ago 
Hi,

In the image provided, the highlighted blue route goes on the highway and then 
back on small roads.  We need a speed file to correct this issue.  The route 
should continue on the green line instead.  Can anyone help with this?

Thank you,

Matt

Original issue reported on code.google.com by RdRunne...@gmail.com on 10 Apr 2012 at 1:39

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GoogleCodeExporter commented 8 years ago 
Hi,

While it might be simple to "fix" this case with another speed profile, it is 
not immediately clear what the best fix would be for you.

First of all you should take a look at the underlying OSM data:
 - What maxspeed does the green line have, what maxspeed does the original route have? You can investigate the data on the OpenStreetMap website: "Edit->Browse Map Data" when you are zoomed in.

Furthermore:
 - Which speed profile did you use?
 - Which "vehicle" are you targeting?
 - Why do you prefer the green line over the original route? Because it is shorter? Would you always want to have the shortest route? MoNav's default speed profiles prefer the fastest route always, i.e., the green line is slower than the blue route.
 - What would be the expected behavior in this case: You have a motorway surrounding a city, and you have the choice between using the motorway a bit, or driving through the city. The first choice is faster by X%, albeit longer by Y%.

Based on your answers I can try to advice you how to construct your speed 
profile. However, this topic is relatively complex in general, since the 
desired "metric" by which a route should be evaluated is hard to specify or 
convert to numbers based on local attributes.

Original comment by veaac.fd...@gmail.com on 10 Apr 2012 at 2:52