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[mkgmap-dev] [PATCH v2] Advanced restrictions

From Marko Mäkelä marko.makela at iki.fi on Sun May 16 07:08:22 BST 2010

On Fri, May 14, 2010 at 04:51:21PM +0100, Paul wrote:
>> What are via ways in restrictions? Could you give some practical example
>> of what they do and what they are needed for?
>> Would they increase the maximal routing distance? Or maybe it the fact
>> that they are missing the reason for our intertilerouting in Mapsource
>> which is not working correctly?
>This is something I brought up a while ago. Consider the following
>A       B       C
>        |
>D      E|       F
>        |
>        \/
>        G
>ABC is oneway in direction ABC
>FED is oneway in direction FED
>BE is twoway but is marked with direction BE
>U turns are not allowed for FEBC nor are they allowed for ABED but all other turn are allowed
>In this situation the "via way" is BE and you create a no_u_turn trstriction from FE, to BC, via BE. Up until now mkgmap would ignore this restriction as it couldn't handle it.
>There are loads of these near me and I suspect in many other places as well

Sure, every place where there is a major road that is mapped as two 
antiparallel oneways. Usually U turns and across-the-ongoing-traffic 
turns would be prohibited, and the 'via' would be a two-node way, not a 


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