[pgrouting-users] Alternate routes (but same cost mechanism)

Charles Galpin cgalpin at lhsw.com
Tue Sep 6 10:52:50 EDT 2011

I have what I consider a bit of a crazy requirement for routing.  In addition to being able to influence the route with rules like shortest path, or fastest, etc. I need to also be able to offer alternative routes within a specific mode.  So say they want to favor or avoid highways, I need to be able to give them a few alternatives as well.

Does anyone have any thoughts on this?  I'm pretty sure even google is doing something like showing you fastest versus shortest, or some other weighting between the options they give in their alternate routes.

I have not played with any of the routing algorithms other than Dijkstra (for some reason I could never get A* to work for me when I first looked at pgRouting but will revisit it) so I am not sure if I can expect them to give different results (or with shooting star even), given the same weighting.

The only think I can think of is to throw "blocks" or penalty wieghts in at random locations  (or somehow come up with a clever way to pick them) and re-route and take the new paths, but I suspect this will be very crude, and not useful anyway.


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