Routing errors in London

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Routing errors in London

Postby dknight212 » Mon Jul 22, 2013 8:44 am

We are picking up quite a few routing errors in London at the moment. In particular routing from S or SW London to N or NW London seems to throw up problems. Some of these may be time dependent. Please can we collect any issues on this in this thread so we can see where the problems are arising. I had a few URs where I was tracking them but some very kind visitors to London have marked them as solved.

I have suspicions that both the A406 North Circular and A10 are involved somehow but no proof. there may be a map problem or some issue with Waze's algorithms on particular routes.

If anyone wants to do some debugging please do! I'm pulling my hair out at the moment, and it's my last one.

Example routes that seem to fail (on live map):

Sutton to Cockfosters
Tooting to Hoddesdon

This route was failing the other day but seems to be working at the moment

Chelsea to Hoddesdon
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Re: Routing errors in London

Postby dknight212 » Mon Jul 22, 2013 8:52 am

Ilford to Twickenham
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Re: Routing errors in London

Postby seriousarsonist » Mon Jul 22, 2013 8:54 am

Hi

I've noticed some weird routing happening over here in NI as well, I'd just put it down to an algorithm problem or something back end but I shall investigate further! will also have a look at your routes although if I find anything you'll have to fix it for me...

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Re: Routing errors in London

Postby dknight212 » Mon Jul 22, 2013 8:55 am

Pip - thanks! Are yours complete routing failures or just odd routes?
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Re: Routing errors in London

Postby Twister-UK » Mon Jul 22, 2013 4:30 pm

Been playing around on LiveMap with southerly routes from Cockfosters.

Routing down to Shepherds Bush, Fulham and Wandsworth all look OK, returning complete routes with every request.

Balham is where things start to fall apart - more often than not this doesn't return any results, and when it does only the route via the A1 actually reaches Balham, the route via the A406 stops short in Battersea.

Wimbledon, Sutton and Croydon appear completely unreachable... some might consider this to be a beneficial side effect of the routing algorithm.

If I then start looking to the east or west, routes become available again to sought-after destinations such as Knockholt and Chertsey, so unlike some other routing problems we've seen in the past this one doesn't appear to be purely distance related.


Returning to Wimbledon as a destination and tweaking the start point shows that routing from Finchley is reliable, yet no route can be found from the nearby Friern Barnet or Bounds Green. A sanity check shows that Bounds Green to Wandsworth is fine.

Bounds Green to Roehampton is OK, as is Bounds Green to Tibbet's Corner. Attempting the extra mile or so to reach Southfields is a no-no. Oddly, Finchley to Southfields is also a no-no, despite Finchley being valid as a starting point for Wimbledon...
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Re: Routing errors in London

Postby dknight212 » Mon Jul 22, 2013 4:51 pm

This is really helpful, thanks a lot.

Do you have any ideas as to whether this is a map or an algorithm based problem?
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Re: Routing errors in London

Postby seriousarsonist » Mon Jul 22, 2013 9:10 pm

dknight212 wrote:Pip - thanks! Are yours complete routing failures or just odd routes?


Bit of both but more the later, checked a few out and they worked then they didn't , so really not sure what is going on. I did check the routes but found nothing untoward bar a few dodgy nodes which I fixed. Will look at some of your routes tomorrow


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Re: Routing errors in London

Postby Twister-UK » Mon Jul 22, 2013 9:44 pm

Checking the above routes from home a few hours later, Cockfosters to Balham, Wimbledon, Sutton and Croydon now all work perfectly. Friern Barnet and Bounds Green to Wimbledon also work fine.

Bounds Green to Southfields is still broken, as are several other randomly chosen starting points, however Bounds Green to a specific road within Southfields is OK.

I'll check again at work tomorrow...
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Re: Routing errors in London

Postby Twister-UK » Tue Jul 23, 2013 6:21 am

Still at home, and now this morning all of the routes that were broken as per my original post, and seemed to be fixed as per my second post, are now broken again... Also broken is Cockfosters to Wandsworth, which is now behaving the same way Cockfosters to Balham did originally - either not returning any route, or returning two routes one of which stops short of the destination.

Cockfosters to Fulham, Finchley, and other destinations closer to the origin, all seem to work OK. Cockfosters to Catford and Brighton also work OK, once again indicating that it's not a simple distance-related bug. The calculation for the Brighton route also took considerably longer than any of the failed route attempts, suggesting also that the routing engine isn't simply timing out whilst trying to generate some of those shorter routes.

Cricklewood to Wimbledon works fine, so it doesn't appear to be a basic problem with the map data itself - between the successful Cockfosters-Fulham and Cricklewood-Wimbledon routes, all of the required segments and junctions have been traversed by one or other of the routes, and with more than sufficient overlap in the middle to avoid any risk of it being a segment/junction somewhere in the Fulham area that might be causing the problem.

To avoid the A406/A10, I also looked at routing due south from Cockfosters. Routes to Kennington and Camberwell come up fine, yet routes to Herne Hill, Dulwich and Sydenham all fail.

I'm thinking algorithm problem at this point - breaking the routes down into smaller chunks allows routing, so it's not a case of incorrectly set segment directions/turn permissions etc somewhere between the overall start and finish points preventing routing at all. Distance, or at least complexity of the route, is somehow involved - as noted above it's not simply a case of "routes > x miles = failure", but perhaps more a case of "routes traversing more than x nodes or requiring more than y instructions to turn from one segment to another = failure". This could account for the longer distance routes (e.g. Cockfosters-Brighton) working OK, as they start to skip large sections of the urban crawl that's required for the shorter routes contained entirely within London, and instead get routed over the trunk roads which offer more miles per node/instruction.
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Re: Routing errors in London

Postby Twister-UK » Tue Jul 23, 2013 9:52 am

Curiouser and curiouser...

To aid repeatability, I've now run some tests placing the start and end points at obvious places on the map. With the start point at the end of Games Lane in Cockfosters, I started generating routes southwards as before.

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This screengrab was taken from an earlier test, hence the route summary box showing a different end point to those mentioned below...

With an end point at the north end of the B219, both the proposed routes are OK.

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However, move the end point just a few yards further to the south, and now the route via the A406 stops short to the north of the A2214... Checking that section of the B219 in WME shows no oddities - it's a single segment between its junction nodes with the A2214 and The Gardens, so moving the end point south like this hasn't added any extra node/junction traversals compared with the route that ends right at the top end of the B219 - this time it's purely the extra distance that seems to be messing things up.

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