Few car owners know of the data-collection devices in their vehicles. While valuable research tools, they may also be threats to privacy.

If you're like most people, you don't know there is a device in your vehicle that, in the event of an accident, stores information about such things as speed, throttle position, braking, and airbag deployment. It can even tell if seatbelts were buckled.

Two-thirds of the new cars sold in the U.S. and some 30 million vehicles already on the road contain such devices, officially known as event data recorders. Information from the black boxes can be critical evidence in criminal cases and lawsuits, helping convict speeders and drunk drivers and exonerate the falsely accused. The auto and insurance industries also believe such data-tracking could be invaluable in improving traffic laws and designing safer vehicles.

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