Dear All,

I am in the process of splitting a large relation (previously 523 members and I understand 300 is the maximum recommended) into a super relation made up of two children. The relation describes a ring road which has twin one-way ways throughout its route. I propose to have one child with all members in the role of "forward" (clockwise righthand carriageway) and another as "backward" (anticlockwise lefthand carriageway). I understand the mechanics of how to do this with JOSM but the question is, what is best practice for the order of the "backward" child? As a trivial example, if the first four members of "forward" are A, B, C, D, should "backward" have the same order or should it be reversed i.e. D, C, B, A?

Many thanks in advance,

Feilipu

asked 12 Apr '13, 00:06

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Feilipu
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accept rate: 10%

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A link to the actual relation might help here, so that people can see the way direction on each carriageway among other things.

(12 Apr '13, 00:56) SomeoneElse ♦

It should be forward and forward, otherwise the anticlockwise left-hand carriageway would be going backwards - Cars don't drive backwards!

The first four members, or the order of each child, should be according to the customary direction of the ways, and the roles of the children relations should both be "forward", hence:

A--->B--->C--->D D--->C--->B--->A

Where letters represent junctions they pass through.

A backwards relation would only be necessary if the route was entirely two-way. Of course a motorway isn't usually two way in the UK. The only one that was a single carriageway that was (A6144(M)) was downgraded some time ago.

permanent link

answered 12 Apr '13, 00:09

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Amaroussi
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edited 12 Apr '13, 03:27

Thanks for the quick reponse but traffic is flowing in opposite directions - there is no question of cars driving backwards. D<---C<---B<---A D--->C--->B--->A

(12 Apr '13, 00:20) Feilipu

Is it a dual carriageway or single? The order for anti clockwise dual carriageways should be DCBA and the role generally forward for the customary direction of the one-way route. Sorry for the hurry but I am nearly going to bed.

(12 Apr '13, 00:21) Amaroussi

It is a motorway in both directions

(12 Apr '13, 00:28) Feilipu

The first four members, or the order of each child, should be according to the customary direction of the ways, and the roles of the children relations should both be "forward", hence:

A--->B--->C--->D D--->C--->B--->A

Where letters represent junctions they pass through.

(12 Apr '13, 00:35) Amaroussi

OK, seems logical. I thought that a backward relation might be used by route finding apps etc. Is it superfluous in this case?

(12 Apr '13, 01:30) Feilipu

A backwards relation would only be necessary if the route was entirely two-way. Of course a motorway isn't usually two way in the UK. The only one that was a single carriageway that was (A6144(M)) was downgraded some time ago.

(12 Apr '13, 01:51) Amaroussi

Thanks Amaroussi, I'm clear now.

(12 Apr '13, 02:16) Feilipu

@Amaroussi - isn't there still the A601(M)?

(12 Apr '13, 11:05) Richard ♦
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question asked: 12 Apr '13, 00:06

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