1. A computer system disposable on a vehicle, comprising: (a) one or more traffic information receivers and transmitters configured to receive and transmit traffic condition information; (b) a system location receiver configured to determine a position of the system; and (c) a signal processing unit comprising a processor and a memory coupled to the one or more traffic information receivers and transmitters and the system location receiver, wherein the signal processing unit is configured to perform the steps comprising: (i) determining a first and a second position of the system along a road segment; (ii) determining an elapsed time between the first and second positions of the computer system; and (iii) determining whether the elapsed time indicates a congested traffic condition along the road segment by comparing the elapsed time with a stored time value for the road segment.