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Network analysis: trouble carrying out closest facility analysis

Question asked by charlottejenkins on Jul 28, 2015
Latest reply on Jul 29, 2015 by charlottejenkins

I’m trying to carry out closest facility analysis in Arcmap 10.2.2 on the network analysis layer created from the OS integrated transport and urban path networks. But when I click "solve" in the network analyst bar, to generate the routes between the incidents (postcode centroids) and facilities (green space access points), its failing to calculate routes for all my incidents.

An error window comes up once the analysis in complete listing hundreds of the incidents which it says are on traversable positions of the network e.g. "Location BS138RG in incidents is on a non-traversable network element position".

Error message after the network analysis has been undertaken, done after clicking "solve"

It repeats this message for 1715 of my incidents, then the list goes on to list 2716 postcodes which it says no facilities can be found for, I assume because of the incidents being on non-traversable parts of the network. All my access points and postcodes were originally located fine when I loaded their locations, shown from the image below. And routes have been calculated fine for about 85% of the incidents, but I can't work out why it's not working for them all, many of the facilities and locations now showing up as errors on the map.

Loading locations of facilities and incidents

I didn't set any restrictions in the analysis settings of the network analysis layer, so assumed this would mean that all parts of the network should be traversable. However, because I set drive time as the impedance, perhaps the problem's that in the speed profile for this impedance, the speeds are set to 0 mph along networks which aren't accessible by cars e.g. paths, bridleways. In which case, perhaps there's no way around some of the incidents being on non traversable parts of the network when calculating drive times, since cars are never going to be able to drive along these types of networks! Or perhaps the problem's that most of my facilities and incidents aren't actually situated on the network. But I thought selecting to "snap to position along network" when loading the locations of each of them, would prevent this being a problem.

I'm very confused as to what's preventing it working so any help would be hugely appreciated!