[OSM-newbies] Question about how to connection correctly highway links

[Sebastian Arcus]

Hi Phil,

Thanks for the extra info. I will download a fresh copy of maps for 
Navit with the restrictions in place to make sure that junction works as 
expected. I kind of figured out Navit's navigation must have thought 
that route would have been shorter or better somehow - but in real life 
it wouldn't have been a viable one.

I must admit I haven't figured out yet the business with trunk roads - I 
always sort of assumed based on OSM's wiki that "A" roads in UK are 
primary highways - clearly I must go back and read the OSM highway 
classification again. It doesn't quite help the fact that tertiary 
highways correspond to "C" roads, and secondary highways correspond to 
"B" roads - thus living primary highways without a direct correspondent 
in UK.

Regards,

Sebastian


On 16/12/12 19:37, Philip Barnes wrote:
> The ahead only restrictions you have added should work, will have to
> wait until Tuesday to see if they have worked in OSRM.
>
> Apart from the missing restrictions, its one of those strange routing
> algorithm things. It is taking that route because it reaches the trunk
> road in a shorter distance.
>
> OSM is based on the UK road classification system, so we have it easy. A
> trunk road has green signs and usually but not always an A number (there
> are B roads that are trunk), in other countries much discussion does go
> into road classification and what is and isn't a trunk road.
>
> Phil
>
>
>
>
>
> On Sun, 2012-12-16 at 11:38 +0000, Sebastian Arcus wrote:
>> I have a question about how to correctly trace highway links at
>> junctions/intersections. Sometimes a link physically crosses over one or
>> two other lanes coming from the other direction of traffic, before
>> reaching the lane it is suppose to merge into. Now, these junction
>> points do exist in real life, but from the point of view of navigation
>> software, they are useless as one is not allowed to turn turn into any
>> of those lanes of traffic it crosses until it reaches the right lane it
>> is supposed to merge into.
>>
>> My question is, should these junction/common points between paths
>> actually exist in OSM? Wouldn't it be better to draw the highway link
>> like it wouldn't actually intersect with those oncoming traffic lanes -
>> and just joined it to the final destination lane? I use Navit GPS - and
>> it sometimes assume I can turn into those oncoming traffic lanes just
>> because the common waypoint indicates there is a joint. Maybe other GPS
>> navigation software does the same mistake?
>>
>> In case my explanation is a bit fuzzy, I will give an example. The
>> following relatively simple junction is in Liverpool:
>>
>> http://www.openstreetmap.org/?lat=53.394271&lon=-2.982713&zoom=18
>>
>> Imagine you are traveling northwards on Sefton Street towards the
>> junction. The right-most link (looking northwards, in the direction of
>> travel) is obviously a no-no as it is a one-way going south. However,
>> Navit suggested for some strange reason that I take the middle link, and
>> then turn immediately left on the first lane of traffic that the link
>> hits into Chaloner St and continue northward. In real life, that is
>> impossible, because that particular highway link (the middle one) is
>> only for crossing over the first two lanes of traffic it encounters, and
>> then merging with the far most one and continuing east on Parliament Street.
>>
>> My thinking was that if the middle link coming from Sefton Street didn't
>> have common waypoints/joints with the first two lanes, the navigation
>> software would have never had any reason to suggest such a move. Those
>> points are as good as non-existent in practice, as they can't be used
>> for turning left or right into those two lanes.
>>
>> Could anybody with more experience weigh in on this with some pro's or
>> con's please.
>>
>> Thanks,
>>
>> Sebastian
>>
>> _______________________________________________
>> newbies mailing list
>> newbies at openstreetmap.org
>> http://lists.openstreetmap.org/listinfo/newbies
>
>
>
> _______________________________________________
> newbies mailing list
> newbies at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/newbies
>


-- 
Linux vehicle CCTV - www.open-t.co.uk/iroko