Motoring Discussion > How do routefinders find their routes? Miscellaneous
Thread Author: Zero Replies: 2
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 Fri 15 Apr 11 20:38 
 How do routefinders find their routes? - Zero
BBC web article, where they used the ultimate route question, one that always has me in a quandary.
The A303 or M4/M5 to Devon/Cornwall.

www.bbc.co.uk/news/magazine-13063738



(The A303 or M4/M5 answer is of course - It depends!)
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 Mon 18 Apr 11 14:43 
 How do routefinders find their routes? - oilburner
I think that article was a touch oversimplified. It doesn't explain how they find their way to the nearest main road for instance, or what happens when you tell it to avoid certain roads and it has to re-route around them.

Interesting though.

This is a good introduction to the theory behind it for those with lots of time on their hands:

en.wikipedia.org/wiki/Dijkstra%27s_algorithm

Warning: possible brain injury may result from reading that wikipedia article!
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 Tue 19 Apr 11 16:21 
 How do routefinders find their routes? - movilogo
It is just "Graph theory" in mathematical terms.

Each road, depending on motorway, B road etc. carry some weightage.

The algorithm selects the shortest/fastest route based on how these weightages are assigned to each roads.

But the algorighm is only as good as data available to it. If map is wrong, then it can calculate wrong direction.
Last edited by: movilogo on Tue 19 Apr 11 at 16:23
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