System and method for geographically locating a cellular phone

A method of monitoring vehicle traffic flow by determining successive locations of a plurality of cellular phones located in a plurality of vehicles, the method comprising:

• repeatedly determining the location of at least some of the plurality of cellular phones;
• and
• sampling the locations of the at least some of the cellular phones to determine a present picture of vehicle traffic flow;
• wherein determining the location of a cellular phone of the plurality comprises determining the area in which handover from a first cell to a second cell occurs, the determination of the area in which handover occurs being based on:
• modeling at least a portion of a cell reception area of said first cell and said second cell;
• and
• defining the area in which handover occurs to comprise overlapping portions of said first and second cell areas.