Dear Doug et al,
I may have missed a crucial message but the
most obvious starting point for solving the
problem of getting from A to B is to use...
Dijkstra's Algorithm
This was devised by the great Dutch Computer
Scientist E.W. Dijkstra in 1959 for finding
the shortest distance between two nodes in
a graph. He was way ahead of GPS!
Nodes in the graph correspond to intersections
and edges or vertices in the graph correspond
to roads. There are good accounts of this in:
http://en.wikipedia.org/wiki/Dijkstra's_algorithm
An over-naive explanation is that you replace
roads by pieces of string and intersections by
knots. You then pick up the two intersections
you are interested in and stretch them as far
apart as you can. The sequence of pieces of
string that are in tension will lead from one
intersection to the other by the shortest
route.
Adapted to real life, distance is better measured
in time rather than miles but the idea is the
same. There are now dynamic GPS systems operating
which change the weights (lengths) of the edges
according to traffic conditions.
Best wishes
Frank
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