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I used to use Dijkstra to find the shortest path between two points. Now I have a shortest route, which uses a street forbidden to use because of internal rules (too slow due to shopping mall).

Now I would like to add a stopover on an alternative road and use a two segments Dijkstra. Is this the best way or should I better work with a turn-restriction network? The latter allows to set the costs for the shortest path / the street in question higher as usual.

The TSP is currently only implemented with Euclidian distance - this is not accurate enough for European street layouts.

  • if it's forbidden why not just take it out of the calculation. Dijkstra's algorithm adapts easily to cost/impedance so you could weight this one heavily so that it's only chosen if it's the only way to get there; then this would give you an option to light weight preferred paths like better/multi-lane roads, such that even if it's not the shortest path a preferred route will be traversed. Perhaps default each line at 1 (for 1 x length) and go 100 for forbidden paths and 0.9 for preferred routes and see how that works out. – Michael Stimson May 17 '14 at 11:26
  • Ok, it is forbidden for the standard route. Nevertheless, it should still be accessible. If I had increased the costs of the edge, I would change the original data and risk increased traveling times in this area. It is possible, but there must be a nicer way keeping the original network untouched...? – Frank May 17 '14 at 11:48
  • Ok, I made a simple manual select ... where gid in (x,y) inside the routing statement. – Frank May 17 '14 at 14:59
  • Please use the edit link on your question to add additional information. The Post Answer button should be used only for complete answers to the question. – Paul May 17 '14 at 15:25
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TSP has 2 alternative ways to be called: one uses the euclidean distance as you said, the second one requires a distance matrix as the first argument:

SELECT seq, id FROM pgr_tsp('{{0,1,2,3},{1,0,4,5},{2,4,0,6},{3,5,6,0}}'::float8[],1);

 seq | id
-----+----
   0 |  1
   1 |  2
   2 |  3
   3 |  0
(4 rows)

It's up to you how to calculate the distance matrix. If you have many stop points, pgRouting's shortest path functions might not be fast enough.

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