-->After seeing the messages about Federal Express doing something similar, -->I thought this would be of interest: Date: Mon, 09 Sep 96 17:41:31 GMT From: campbellp@logica.com (Peter Campbell Smith) Subject: Re: Locating the position of cellular phones (Stover, RISKS-18.41) There is an interesting article in Traffic Technology International, Aug/Sept 96 issue about a system called CAPITAL that uses cellular phone calls as a probe to monitor road traffic around Washington DC. It describes an experiment which has been running for two years and which has demonstrated that this is an extremely cost-effective alternative to conventional means of traffic monitoring. The system is independent of the cellular phone system per se, but has antennae on the cellular phone masts which listen to the cellular frequencies. Every time a call is initiated, CAPITAL locates the caller by a combination of directional multi-element antennae and time-of-arrival analysis between different masts. The geographical accuracy is reported to be to about 115m, and subsequent tracking allows the speed of the vehicle to be established within 30 to 50sec to an accuracy of 5mi/h. At any time only less than 5% of vehicles are making calls, but this is a sufficient sample for analysing the traffic speed (though not presumably the traffic density). Moreover, when the traffic slows down even more people make calls, so there is a better density of data from the areas most interesting to those monitoring traffic flows. It is claimed that the boxes ignore the voice content of the call and that the data they deliver has randomly assigned identifiers for each call, so that nothing leaves the system which would allow calls to be associated with specific phones. -->Until the government thinks it needs the info! Peter Campbell Smith, Logica, London, UK campbellp@logica.com