http://groups.csail.mit.edu/drl/wiki/images/0/0e/lim-IJRR2011.pdf

A recent survey (Schrank and Lomax 2007) estimates that the annual nationwide cost of traffic congestion is US$78 billion, including 4.2 billion hours in lost time and 2.9 billion gallons in wasted fuel.

Given the probability distributions of delays on segments, finding good paths requires more than a shortest-path computation, because the ‘optimal substructure’ property does not hold as explained in Nikolova et al. (2006a) (i.e. if the best path from S to T goes through X , it does not follow that the sub-path of this path from S to X is itself the best S–X path).

Stochastic motion planning and applications to traffic (2008, 2010, 2011)